Major corporations raise capital by selling shares in themselves. So do companies with little or no substance behind them. Even startups sometimes "go public" before they really start up. So why can't America's homeowners?

They can. In yet another new twist on the age-old concept of shared appreciation, they soon may be able to raise money for a down payment, or build up enough equity to jettison a higher-rate mortgage for a less expensive one, by "selling" shares in their homes.

Under the plan on the table from PRIMARQ, a San Francisco-based marketplace facilitator that acts much like a stock exchange, owners or buyers would decide what share of the gain in the value of a house -- or of the loss, if values tumble -- they would like to sell to investors.

If, say, you want to buy a $300,000 house, the requisite 20 percent down payment would be $60,000. If you were short half of that sum, you could sell "shares" in the place to raise the necessary funds. Or, if you are underwater and need $30,000 in equity so you can refinance into a loan you can afford, you could sell shares to investors willing to gamble that you can sustain yourself going forward.

Using the PRIMARQ platform, you would list your shares for sale at $10,000 each. And investors would bid on those shares -- each $10,000 unit of currency called a "Q" -- based on any number of variables, including location and anticipated rate of appreciation.

A good property in a sound location in a desirable part of the country would tend to draw more or higher bids than those in other places. And once PRIMARQ takes a 5 percent share for its troubles, you get the rest.

You can live in the property as long as you like; there is no minimum requirement. But once you sell, you fork over the investors' share of the profits -- maybe 40 percent of the gain for a 20 percent share -- and off you go. If there is a loss, you and your investor split that in the same way.

During the time you own the house, meanwhile, PRIMARQ intends to make a market for the shares you sold off, either to one individual or perhaps several, again at $10,000 a crack. The shares can and will be traded among investors, so the ones who were with you in the first place may not be there at the end.

An investor might want to cash out midway through your ownership. Maybe he's found a better place than housing to stash his cash, or perhaps his circumstances have changed. But no matter, you are not impacted in any way. Whether investors resell their shares or hold them, you can go on living in the place as long as you like.

PRIMARQ calls its program a market-based "fresh approach" to bringing private capital into residential real estate, which is perhaps the country's largest asset class. Founder and CEO Steve Cinelli calls it a "paradigm shift" in housing finance.

Whether that is true remains to be seen, for the company has yet to do its first deal. And it's not like there aren't plenty of low-down-payment loan products available on the open market.

Company spokespeople say the initial transaction with a yet-to-be identified "lending partnership" is imminent. But until that deal is announced, there are many unanswered questions.

For one thing, will mainstream lenders warm to the idea that borrowers have less of their own money invested in the property? When hard times hit, banks worry, it could be easier for borrowers to walk away.

Another concern: Will people use the concept to purchase more house then they can afford? And then, there's this: Giving away appreciation is an expensive way to obtain funds for a down payment.

On the flip side, though, you can save a lot of money if you allow investors in on your deal. Say, for example, you can come up with just a 15 percent down payment on the $300,000 house you truly covet. That's $45,000. Typically, with anything less than 20 percent down, you'd have to pay for private mortgage insurance (PMI). So your payment for principal, interest and PMI on a 30-year, $255,000 loan at 4.25 percent (including closing costs) would be $1,686.

Now suppose you use PRIMARQ to raise half of a 20 percent down payment, or $30,000. You'd save roughly $15,000 in cash out of your own pocket because you'll be putting up $30,000, not $45,000. Not only that, but your loan amount would be $240,000 and PMI would no longer be required. So your monthly payment would drop to $1,505. That's a difference of $180 a month.

For that $15,000 you needed from investors to make the deal happen, you might have to give away a 35 percent stake in any gain you realize during the time you own the house.

If you want to sell in five years and the place has grown in value at a 4 percent clip per year, the house would be worth roughly $365,000. You'd owe the lender $217,662. Less that and an estimated $21,900 in selling expenses and you'd be left with $125,500 or so to split with your investor.

Here's where it gets tricky, though, because first the investor would get back his $30,000 initial investment and you'd get back your $30,000 down payment. That leaves $65,000 to be shared, 35-65, or $22,900 to the investor and $42,100 to you.

Now add them together and that's $42,100 plus $30,000 to you, or $72,100. And it's $30,000 plus $22,900 to the investor, for a total of $52,900.

If there's a loss, meanwhile, you have the same percentage split. So if you sell your $300,000 house for $270,000, the lender still gets his $217,662 and you'd still have $21,900 in selling costs. That leaves proceeds of $30,438, or $19,800 or so to you and $10,638 to the investor.

As always, the devil is in the details. These are rough approximations based on an example supplied by PRIMARQ. But the big question is, should you -- can you -- bite the bullet now by making a larger down payment and living with a larger mortgage payment? If you can, you retain all of the gain on the eventual sale, not just a part of it.

A New York developer may be the first homebuilder to integrate wellness into its products. But if a major real estate education and research group has its way, healthy living will soon be incorporated in many of the places where we live and work.

The Urban Land Institute is embarking on a two-year effort to educate its members and the development community at large on how they can build healthy communities and workplaces where people can thrive.

"We are looking at city building through the lens of health and wellness as a way to measure sustainability and long-term prosperity," says Lynn Thurber, chairman of the Washington-based nonprofit. "With this effort, wellness is the intent, the designed outcome, not just an additional benefit."

Delos Living is already pioneering the merger of housing and health, marrying science and architecture to place well-being at the heart of design and construction. Its New York City apartments feature, among other things, a water purification system, floors laid upon a layer of cork and rubber to reduce stress, juice bars and soy-based insulation.

And co-founder Morad Fareed thinks more builders should be integrating medicine into their products to help prevent disease, improve occupants' energy levels and lengthen their life spans. "Why stop at building just houses?" asks Fareed.

In the face of withering sales during the economic downturn, many resort communities have placed wellness above golf and other amenities over the last few years as a way to entice more buyers. But otherwise few residential builders and developers -- or commercial office building developers, for that matter -- have seen the need.

But consider these stats from ULI:

-- By 2030, more than one out of every 11 Americans will be at least 100 lbs. overweight.

-- The cost to treat illness currently consumes 19 percent of America's gross domestic product.

-- 13 million school days are missed annually due to asthma-related illness.

At the same time, ULI says the ability to deliver on health directly translates into market value, and therefore, "makes good building sense." Here's proof:

-- Nearly two-thirds of Gen Y-ers think proximity to a park is an important buying consideration. And three out of four feel the same about walkability.

-- Homes located in neighborhoods with good walkability are worth $34,000 more on average than similar places in neighborhoods with average walkability.

-- A dozen bicycles can fit into one parking space.

-- More than half of us want to live in a community that has transit.

"This is not just about building a walking trail or upgrading a fitness center," says Patrick Phillips, CEO of the Washington-based ULI. "Building healthy places is about improving all aspects of the environment in which people live, from the air we breathe to the places where we work."

To educate and encourage the real estate community to rethink what, where and how it builds, ULI has published as a first step a report outlining the "Ten Principles for Building Healthy Places and Intersections." The report examines how urban design and development can contribute to living environments that are conducive to prosperity.

Here are the 10 tenets of creating healthy places:

-- Put People First -- Health should be a priority, not an add-on or afterthought.

-- Build Economic Value -- The various aspects of wellness lead to greater marketability, quicker sales and greater property values.

-- Champion Health -- Community engagement is a powerful link between health and local land use and bringing about change.

-- Share Spaces -- More public spaces are advocated, as are "living streets," which prioritize pedestrians and cyclists over cars.

-- Make Health Easy -- Make health the one safe, easy choice by, among other things, removing barriers that lead people to default to an unhealthy practice.

-- Build Equitable Access -- Make healthy choices accessible to all income and demographic groups. These include neighborhoods with housing options for all ages and holistic transit plans that reduce the reliance on the automobile.

-- Mix It Up -- Integrate a range of uses -- residential, commercial, cultural and institutional.

-- Create Character -- Places that are different, unusual or unique can help promote physical activity and emotional well-being.

-- Healthy Food -- Diet is a major part of health, so access to healthy food should be part of any development proposal. This means assigning food the same prominence as, say, open space or housing mix.

-- Build Active -- Designs should be used to create active communities -- locating adult and children amenities together, for example -- to boost physical activity and reduce the reliance on cars.

If the nation's homebuilders and office developers take even just a few of these principles to heart, the places where we live and work should soon become much more healthy and enjoyable.

A New York developer may be the first homebuilder to integrate wellness into its products. But if a major real estate education and research group has its way, healthy living will soon be incorporated in many of the places where we live and work.

The Urban Land Institute is embarking on a two-year effort to educate its members and the development community at large on how they can build healthy communities and workplaces where people can thrive.

"We are looking at city building through the lens of health and wellness as a way to measure sustainability and long-term prosperity," says Lynn Thurber, chairman of the Washington-based nonprofit. "With this effort, wellness is the intent, the designed outcome, not just an additional benefit."

Delos Living is already pioneering the merger of housing and health, marrying science and architecture to place well-being at the heart of design and construction. Its New York City apartments feature, among other things, a water purification system, floors laid upon a layer of cork and rubber to reduce stress, juice bars and soy-based insulation.

And co-founder Morad Fareed thinks more builders should be integrating medicine into their products to help prevent disease, improve occupants' energy levels and lengthen their life spans. "Why stop at building just houses?" asks Fareed.

In the face of withering sales during the economic downturn, many resort communities have placed wellness above golf and other amenities over the last few years as a way to entice more buyers. But otherwise few residential builders and developers -- or commercial office building developers, for that matter -- have seen the need.

But consider these stats from ULI:

-- By 2030, more than one out of every 11 Americans will be at least 100 lbs. overweight.

-- The cost to treat illness currently consumes 19 percent of America's gross domestic product.

-- 13 million school days are missed annually due to asthma-related illness.

At the same time, ULI says the ability to deliver on health directly translates into market value, and therefore, "makes good building sense." Here's proof:

-- Nearly two-thirds of Gen Y-ers think proximity to a park is an important buying consideration. And three out of four feel the same about walkability.

-- Homes located in neighborhoods with good walkability are worth $34,000 more on average than similar places in neighborhoods with average walkability.

-- A dozen bicycles can fit into one parking space.

-- More than half of us want to live in a community that has transit.

"This is not just about building a walking trail or upgrading a fitness center," says Patrick Phillips, CEO of the Washington-based ULI. "Building healthy places is about improving all aspects of the environment in which people live, from the air we breathe to the places where we work."

To educate and encourage the real estate community to rethink what, where and how it builds, ULI has published as a first step a report outlining the "Ten Principles for Building Healthy Places and Intersections." The report examines how urban design and development can contribute to living environments that are conducive to prosperity.

Here are the 10 tenets of creating healthy places:

-- Put People First -- Health should be a priority, not an add-on or afterthought.

-- Build Economic Value -- The various aspects of wellness lead to greater marketability, quicker sales and greater property values.

-- Champion Health -- Community engagement is a powerful link between health and local land use and bringing about change.

-- Share Spaces -- More public spaces are advocated, as are "living streets," which prioritize pedestrians and cyclists over cars.

-- Make Health Easy -- Make health the one safe, easy choice by, among other things, removing barriers that lead people to default to an unhealthy practice.

-- Build Equitable Access -- Make healthy choices accessible to all income and demographic groups. These include neighborhoods with housing options for all ages and holistic transit plans that reduce the reliance on the automobile.

-- Mix It Up -- Integrate a range of uses -- residential, commercial, cultural and institutional.

-- Create Character -- Places that are different, unusual or unique can help promote physical activity and emotional well-being.

-- Healthy Food -- Diet is a major part of health, so access to healthy food should be part of any development proposal. This means assigning food the same prominence as, say, open space or housing mix.

-- Build Active -- Designs should be used to create active communities -- locating adult and children amenities together, for example -- to boost physical activity and reduce the reliance on cars.

If the nation's homebuilders and office developers take even just a few of these principles to heart, the places where we live and work should soon become much more healthy and enjoyable.