It's not only the U.S. population that's aging, it's also their houses. More than 40 percent of American homes are more than four decades old.

"A large portion of our housing stock was constructed during the '60s and '70s," says James W. Hughes, a professor and housing expert at Rutgers University.

Despite the current surge in renovation and reconstruction, many of the country's more than 100 million properties have a distinctly dated feel -- both on the exterior and the interior.

The problem for the sellers of these older homes is that facades and floor plans that once appealed to buyers are no longer in favor, particularly with the millennial generation.

"Flow is what it's all about for people in their 20s and 30s," says Tom Early, a veteran real estate broker and past president of the National Association of Exclusive Buyer Agents. "They like high ceilings and expansive floor plans. They hate the boxed-in feel that comes with low ceilings and a lot of small rooms."

For example, typical young buyers crave a large kitchen that opens onto an expansive "great room." They also look for a spacious master bedroom that connects to a well-appointed 'ensuite' bathroom.

Of course, when it comes to the tastes of millennial buyers, there are exceptions to the rule, says Sharon L. Ellsworth, a real estate broker and co-owner of a Re/Max Realty office.

"Some purchasers really appreciate the clean lines of mid-century contemporary houses," Ellsworth says.

But if you're seeking to sell a very ordinary and not-very-attractive house built decades ago, you'll need to factor its age into your decision on pricing, says Eric Tyson, co-author of "House Selling for Dummies."

Here are a few pointers for sellers:

-- Get a grasp on how your place looks to others.

Those seeking a candid assessment of their home's exterior appearance may wish to poll relatives, Ellsworth suggests.

"More than your friends, your relatives will give you their honest opinion. This can be helpful when you decide what price to ask," she says.

-- Highlight the positive in your marketing materials.

"Rarely does a house sell on advertising alone," Ellsworth says.

Even so, creating effective marketing materials can help draw people into a property they might otherwise be unwilling to visit due to its lack of street appeal.

"Pick out the two or three strengths of the house and be sure your agent highlights these in your marketing," says Tyson, the real estate author. "Maybe you have wonderful natural light, or a beautifully wooded backyard. Think back to the factors that drew you to the house when you first saw it," Tyson says.

If your house is located close to a highly rated public school or is set in a walkable urban area, those are also strong selling points.

-- Consider hiring a photographer.

More than ever, buyers are previewing properties online. It's not unusual for a listing agent to post between four and 10 photos of a house on the Internet.

Your agent may be skillful at taking photos with a cell phone. But if your home shows poorly from the street, Tyson says you could still do better with a professional photographer.

Your listing agent may ask you to cover the photographer's fees. Yet Tyson says the money could be well spent if it brings in prospects who might otherwise fail to visit the place.

-- Request that your listing agent conduct one or more "broker's opens."

Most people are familiar with public open houses, where anyone can show up. But Tyson says a more effective sales tool is a "broker's open," limited to real estate agents from the surrounding area.

"These kinds of open houses are incredibly important. That's because the vast majority of serious buyers still work with agents. If agents come through the house and like it, they're more likely to show it to their clients," Tyson says.

-- Add appeal to your property with a new front door.

It's rare for listing agents to recommend major upgrades to the exterior of a home in order to sell it, but one upgrade that can prove worthwhile is a new front door. The cost: perhaps a few hundred dollars at most.

"The front door is the focal point of the house. If it's attractive, people will focus on this," Ellsworth says.

If you don't want to spend the time or money to replace your front door, consider other, less costly steps, such as repainting the door or adding new polished brass hardware.

-- Emphasize highly visible upgrades.

Not all sellers have time to make surface enhancements to their home, especially if they're making an urgent move. But those with sufficient time -- and funds -- generally more than recoup their expenses, Ellsworth says.

Flowers, new greenery and freshly pruned shrubs help entice buyers who might otherwise refuse to venture inside. Also, outlays for interior painting, carpet replacement or hardwood floor improvements are typically worth doing, as is replacement of outdated kitchen appliances.

"Very visible improvements could pay you back several times over," she says.

(To contact Ellen James Martin, email her at ellenjamesmartin@gmail.com.)

John Rygiol, a real estate broker who's worked with homebuyers since 1971, has a few words of advice for home sellers and their agents: Remember that first impressions count.

"It just blows me away when sellers fail to fix little things that are huge turnoffs to buyers," says Rygiol, who specializes in the sale of upper-end properties.

One of his biggest beefs is with sellers who have broken or tricky front door locks that frustrate buyers even before they step into a place.

"Everyone's time gets wasted, and the buyers get hopping mad," Rygiol says.

Another gripe: sellers with noisy or bothersome pets.

Another turnoff is a house so cluttered with collectibles that buyers can't appreciate the sizes of the rooms or picture themselves living there.

Savvy sellers should not only address these troublesome issues but also take proactive steps to make a property welcoming, says Sid Davis, a veteran of the real estate business and author of "Home Makeovers That Sell."

Here are a few pointers for sellers:

-- Repair or replace faulty front door locks.

Rygiol is hardly the only real estate broker who underscores the importance of well-functioning front door locks. Another is Merrill Ottwein, a former president of the National Association of Exclusive Buyer Agents (naeba.org).

"When the lock doesn't work, this conveys indifference on the part of the sellers and alerts buyers to the prospect of more serious problems within," Ottwein says.

Assuming you have two or more locks on your front door, he recommends you eliminate all but the deadbolt.

"Redundant locks drive a lot of people crazy," he says.

While you're at it, double-check that your doorbell is working perfectly.

"Like a malfunctioning lock, an out-of-repair doorbell is a big turnoff," Ottwein says.

-- Surround your entrance with attractive landscaping.

For those wishing to make a powerful impression on potential buyers, good landscaping is a must, Ottwein says.

One common error committed by sellers is to allow their bushes and other plants to grow too tall or too close to the front walls of the house.

"This obscures the view of the house from the street. The place looks cramped, as if the greenery has been shoehorned in," Ottwein says.

Creating the right landscaping doesn't require an expensive designer. But it may mean removal of trees that are positioned anywhere in the front yard so as to hide the home.

"To me, the definition of a weed is any plant or tree that's out of place," Ottwein says.

-- Make your front door beguiling.

As Ottwein says, the front door of a home can either attract or repel visitors.

Often, the owners of homes that are well kept inside are scarcely aware that their front doors look shabby, he says, because they habitually enter through a back door or the garage. But buyers will undoubtedly come in through the front.

"It's usually not expensive to greatly improve the look of your front door, unless you have a big mahogany door that needs replacing," Ottwein says.

A thorough cleaning and removal of cobwebs in and around the front door is virtually free, but for the expense of cleaning supplies. And a door that merely suffers from peeling paint can usually be redone for under $100.

-- Welcome visitors with pleasant aromas.

Ottwein, a former veterinarian turned real estate broker, is very favorable to pets. Still, he cautions that the smell of animals in a home can repel buyers as quickly as any other factor.

"A lot of people try to use spray fresheners to cover animal smells, cigarette smoke or other bad odors. But air fresheners can be overwhelming and create a very negative impression, like a woman wearing too much perfume," Ottwein says.

A home that is thoroughly clean and devoid of pet problems and mold issues should also be free of odors --assuming nonsmokers inhabit it.

"You don't need to spray anything in your house to make it smell fresh, which is perfect in and of itself. Beyond that, the only positive would be to have the scent of freshly baked cookies or bread circulating in the air," Ottwein says.

-- Enhance your place with flowers.

There's a good reason why flowers are the primary decor items used at weddings and other elegant events. They create a qualitative difference that no other design element can match -- not even the most remarkable furnishings or works of art.

Potted flowers add welcoming appeal when placed alongside the front door of a house. Also, bouquets of cut flowers can make an otherwise unremarkable home interior look extraordinary.

It can be pricey to keep your vases filled with fresh flowers throughout the time period when your property is being shown for sale. But fresh flowers create so classy an impression that many sellers consider flowers their secret weapon.

"Why bother with fake flowers? This is the biggest sale of your life, so it's foolhardy to shortchange yourself on this expense," Ottwein says.

(To contact Ellen James Martin, email her at ellenjamesmartin@gmail.com.)

Tom Early, a real estate broker since 1981, has seen a distinct trend across the decades. These days a woman is more likely to insist on keeping a home she bought before marriage -- even after partnering with a man who already owns a place.

"Sometimes a career woman refuses to surrender her property," says Early, a past president of the National Association of Exclusive Buyer Agents. "She's earned that home and it's her trophy. That's the same way many men feel about their cave."

Of course, not every marrying couple can afford to keep two homes. And couples who plan to have children together usually favor living full-time under one roof. But empty nesters on their second marriage now occasionally opt for two domiciles, so long as they can see each other on weekends and vacations without undue hardship.

"Let's face it, most people aren't jet-setters like the celebrities in People magazine who marry but still keep her place in New York and his in Los Angeles. Besides, very few people want to live that far from a mate," Early says.

Even so, there are legitimate reasons why some couples wish to keep their two homes after the wedding. One is that very often partners -- who are committed to their respective careers -- originally bought properties near their places of work.

"Suppose she owns a house near her office in Minneapolis and he has a condo walking distance from his job in St. Paul. This is one couple who might decide to keep both the condo and the house and then rendezvous on weekends," Early says.

Alternatively, such a couple might split the difference, sell both properties and buy a place together that's midway between the two Minnesota cities.

But Mark Nash, author of "1001 Tips for Buying & Selling a Home," says more couples are now opting for a two-city lifestyle.

"We're getting away from what we used to call 'the trailing spouse.' Now each partner wants to keep what they have going into the relationship," he says.

In some instances, dual-city homeownership can enhance the romantic life of spouses who live separately on weekdays and then reunite at week's end, says Esther Perel, author of "Mating in Captivity: Unlocking Erotic Intelligence."

The weekends "can be a wonderful reunion time for some couples," Perel says.

Of course, there can be pitfalls in the dual-city approach to homeownership. Here are a few pointers:

-- Consider the implications if young children are involved.

Perel cautions that such a situation can add stress when one or both partners are parenting infants, toddlers or school-age kids.

"This living arrangement can become burdensome to the person who manages the children during weekdays," she says, adding that this situation can lead to resentment in the partner who's shouldering more responsibility.

Also, she says kids who grow up with parents who live in two households may be shortchanged the kind of nurturing they need to thrive -- even if the parents are happily married.

-- Think twice about the impact of added travel.

"All that travel back and forth can become tiresome on the relationship," Perel notes.

Travel costs can also mount up.

"People sometimes forget to add up the full cost of commuter marriages in both time and money," Nash says.

-- Factor in the financial consequences beyond travel costs.

When considering expenses associated with the ownership of two homes, Nash says you should always look beyond the cash flow implications of carrying two mortgages. Also make sure you add in the extra costs you'll likely face for insurance, taxes, repairs and maintenance.

To assess the full financial implications of dual-city homeownership, Nash recommends you consider meeting with a trusted financial planner who's paid on a fee-only basis, rather than from commissions on the sale of stocks or insurance.

"Look for someone who can objectively evaluate whether it's prudent to keep two homes -- not a planner who will try selling you lots of financial products," Nash says.

One way to find a fee-only planner in your area is to visit the website of the National Association of Personal Financial Advisors: www.napfa.org. Also, you can find fee-only planners willing to work with you for just an hour or two by visiting the website of the Garrett Planning Network: www.garrettplanningnetwork.com.

-- Realize the possibility that distance could enhance your relationship.

Couples who choose to live in two homes are taking a non-traditional route. But, as Nash says, this avenue could be one that maintains the quality of life for one or both partners -- especially if it results in professional fulfillment and their two properties appreciate in value over time.

Also, Nash says he knows a number of two-house couples who've avoided the kind of bickering that sometimes troubles those who live together all the time.

"As the old expression goes, 'familiarity breeds contempt.' But when you see each other only on weekends and vacations, you're less aware of each other's flaws and more aware of the love that brought you together in the first place," he says.

(To contact Ellen James Martin, email her at ellenjamesmartin@gmail.com.)