San Francisco may be a nice place to visit, but who among us can live there?

While the City by the Bay has some wonderful attributes and attractions -- the Golden Gate Bridge, sourdough bread and Alcatraz, among many others -- it also has the largest concentration of million-dollar homes of anywhere in the country.

According to search engine Trulia, 58 percent of the houses in the San Francisco metro area are worth $1 million or more. In the city proper, 63 percent of the houses are valued at least a million bucks -- the highest percentage in the nation. That's more than 3 in every 5 houses.

Two other Bay Area spots, San Jose and Oakland, rank second and third on the list, respectively. In San Jose, 43 percent of the houses are worth at least $1 million; in Oakland, it's 18 percent.

The number of vacant foreclosures is down 43 percent from a year ago, according to housing data bank RealtyTrac. The group says the war on vacant, so-called "zombie" foreclosures is being won.

At the same time, though, of the 1.5 million vacant residential properties nationally, 98 percent are not in foreclosure or even underwater.

Of the 84.7 million U.S. residences, 1.5 million were empty as of the end of September. But at last count, Trulia says vacant homes in the foreclosure process account for 1.3 percent of all vacant residential properties, and bank-owned homes that have been taken back by lenders accounted for 1.9 percent.

According to RealtyTrac economist Daren Blomquist, the overall inventory of homes in the foreclosure process has dropped 36 percent over the past year, so it's "not too surprising" to see a similarly dramatic drop in "zombie" foreclosures.

But what is surprising is that there are so many vacant homes where the homeowners do not appear to be in financial distress. "More than 63 percent of these vacant homes are not even encumbered by a loan; (they're) owned free and clear by the owner," Blomquist says.

"The fact that the homeowners are not selling, given the recovering real estate market in most areas, indicates that many of these properties are in poor condition and in neighborhoods that have been left behind by the housing recovery."

The days when people wouldn't dream of buying a house without seeing it first may be dwindling.

"With all of the technology we now have access to, you can get a comprehensive feel for a home without ever stepping foot in it," say the folks at Homes.com, an online listing service. "And more and more people are doing just that."

According to the latest National Association of Realtors' profile of homebuyers, 92 percent used the Internet to search for homes; 43 percent actually found the house they bought online.

Research by realty brokerage Redfin found that 21 percent of people responding to a recent survey made an offer on a house without seeing it in person. But NAR's latest figures show that less than 0.5 percent of all buyers bought their home sight-unseen.

Either way, though, there's no question that technology is playing a larger role in the real estate purchase. And why not? Sites like Homes.com now offer an all-inclusive home search that some predict will make going to see a house in person the exception, rather than the rule.

First, you can check out a photo gallery of the house, including street, aerial and map views. You can take a virtual tour and read all the property details, including lot size, when the place was built, property taxes, school districts and a whole lot more. Some sites will allow you to compute your commute times, and a few will offer your probable monthly costs, including utilities, association fees and insurance.

The latest wrinkle comes from CubiCasa, which is offering agents and listing services 3-D floor plans of houses for sale. The Bay Area company says it can turn any type of source file, even a hand-drawn image, into a usable floor plan with a guaranteed 24-hour turnaround. That would make visualizing a home's interior spaces easier than ever.

A portent of things to come: Major production builder Lennar has started an "affordable" house community in Austin, Texas, in which all the homes will include solar power as a standard feature.

The 120 houses in the first phase of Colorado Crossing are priced at about $200,000, but the solar panels add nothing to the cost, according to Lennar. Rather, owners will pay a "low, flat" monthly fee to the SunStreet Energy Group, the Lennar subsidiary that works with installers and monitors the rooftop systems. The solar panels are expected to generate about half of the homes' electricity needs.

Lennar currently has about 100 communities under development. Stay tuned.

Most people spend more than 50 percent of their time indoors -- children, some 90 percent -- so it is important to pay attention to the quality of the air in your home. And that means more than installing a few carbon monoxide detectors or testing for radon.

Mold can cause severe health problems, for example. Ditto for lead, a tainted water supply or hazardous household products. And since government at the state and federal levels can only legislate so much, it is up to homeowners to take whatever action is necessary to protect their families.

Indoor air pollutants come not only from what people have in their homes but also what they do there. It is well established, for example, that smoking can cause breathing problems. But so can furry pets and home projects that involve sanding, welding, painting or solvent chemicals like varnish and paint strippers.

Fortunately, there are simple steps you can take to find out the causes of poor indoor air quality and what to do about them.

-- Mold, sometimes known as mildew, grows where there are wet or damp surfaces. You can spot it easily when it grows out in the open, but often it is hidden behind walls or under the carpet. Either way, the telltale signs are the same: musty smells, watery eyes, runny noses, sneezing, itching, wheezing, headaches and fatigue.

To protect against mold, be sure your gutters are clean and not leaking, and that downspouts direct rainwater away from the house. Your yard should slope away from the building.

Repair leaking roofs, walls, doors and windows right away. Water is insidious, and can cause problems if left to stand. If your carpet remains wet for more than a couple of days, for example, it is best to toss it. It's also wise not to leave water standing in refrigerator drip pans.

Additionally, make sure the humidity in your home is not too high. If the moisture content in the air is more than 50 percent, turn off your humidifier and move your jungle of houseplants outside. Always make sure to run your bathroom fan when bathing or showering, and run your kitchen exhaust fan when cooking.

-- Unlike mold, you can't see, smell or feel carbon monoxide (CO), a deadly gas that can make you sick or even kill you. Signs of low-level CO poisoning include headaches, nausea, vomiting, dizziness, sleepiness, tightness in the chest and difficulty breathing. Many people confuse it with the flu.

To protect your house and family, install carbon monoxide alarms near each sleeping area and on each floor. But to make sure they never go off, never use the kitchen stove or oven to heat your house, and call a repair service if the flame on your range's gas burners is orange or yellow.

Also, don't use charcoal grills or run car engines inside your house, garage or basement -- even for a short time. They produce so much CO that even opening the windows and doors will not give you enough fresh air. In the same vein, never warm a vehicle while it sits inside the garage, even with the garage doors open. Start lawnmowers, snowblowers and other yard equipment outside, never inside.

At least once a year, hire a heating contractor to check your furnace, vents and other sources of carbon monoxide. Make sure your fireplace chimney is clean and in working order with an annual checkup.

-- Lead poisoning poses a serious health risk for children. Lead is not used as much in paint, pipes and other materials as it once was -- indeed, lead paint was banned in 1978 -- so houses built prior to 1950 are the most problematic.

If you are planning to remodel your older home, or have just finished a renovation, beware of lead dust or paint chips. Otherwise, look for cracking, chipping or flaking paint, or doors or window frames where paint is being rubbed away.

Also check for lead pipes, which are a dull gray in color and scratch easily with a key or penny, or pipes joined with lead solder. Water that flows through them can contain lead.

Your state or local health department can tell you how to check for lead at little or no cost, and most hardware stores carry low-cost lead testing kits. But if you find lead, don't try to remove it yourself. Getting rid of lead in the wrong way can make the problem worse, so find a certified contractor for the job.

-- Public drinking water is safe, but if you have a well or other private water supply, it's up to you to protect yourself. And since you can't see, smell or taste potentially dangerous microbes, you should have your H2O tested about every two years for bacteria, nitrates and perhaps pesticides at a laboratory.

You should also take care of your well. Have it checked by a professional if it is more than 20 years old. Make sure there are no gaps between the well casting and the material or ground around it.

-- When it comes to hazardous household products, buy only what you need, and read and follow the directions. Properly dispose of what you don't use, or give the leftovers to someone who can use it. Never burn or dump leftover containers.

Most of the information for the above comes from the Department of Agriculture's National Institute of Food and Agriculture (nifa.usda.gov). Other good sources include the Office of Healthy Homes within the Department of Housing and Urban Development (hud.gov/healthyhomes), the Environmental Protection Agency (epa.gov/iaq) and Healthy Indoor Air for American Homes (healthyindoorair.org).

You should never be afraid to make a low-ball offer on a house. But when you know there will be competing bids, that tactic is off the table.

Instead, you've got to work with your agent to come up with your absolute best offer. Remember, others will be doing the same, so you want your offer to be perfect in every way so that it will stand out above the rest.

First, remember that everything is negotiable. Everything! Try to figure out what is important to the seller and use it to your advantage.

If the seller is proud of the beautiful dining room chandelier, offer to let him take it with him. If he says he hasn't found another place to live yet, or his newly built house won't be ready for three more months, give him that time by offering to delay closing for up to 120 days. Your willingness to give the seller the extra time he needs may just be the deciding factor in whose bid he chooses. Alternatively, you could offer to close quickly, and then rent the place back to him until he can move out.

The more you bow to the seller's side, the better. For example: Don't ask the seller to pay for any of your closing costs, or even the amount that is customary in your market.

A somewhat controversial tactic is to attach a personal letter -- maybe even a family photo -- to the offer. It should be handwritten, not typed, and tell the seller how much you love the house and how well you would take care of it. Some sellers have been swayed by this maneuver, even taking lesser offers because they believe the house they love -- the house they really hate to leave -- will be in good hands.

But on the flip side, if the seller knows how badly the buyer wants her place, she might play hardball and refuse to negotiate. In other words, the letter could backfire and put the buyer at a distinct disadvantage.

Say, for example, the seller accepts an offer with a personal letter attached, and a subsequent home inspection finds several issues that must be addressed. The buyer may be willing to bargain on these items, but the seller might not budge, knowing how much the buyer wants the deal to go through.

A few other tips:

-- Escalate. If you really, really want the place, considering adding an "escalation clause." With this tactic, your offer says that if anyone beats your bid, you will up the ante by a certain amount. So if a competitor offers, say, $250,000, you will automatically go to $250,100.

A hundred bucks may not be enough to save the day; $1,000 may be a better figure. Be careful, though. It is wise to set an upper limit in these clauses. Realize, too, that if your bid goes too high, the property may not appraise for what you're paying.

-- Clean your offer. To catch the seller's eye, make your offer as clean as possible: in other words, no contingencies. Don't, for example, make your offer dependent on the sale of your present residence.

There are two clauses you should keep, though: (1) A clause that makes the deal dependent upon your ability to obtain financing at a certain amount and/or interest rate, and (2) A clause that makes the sale contingent on a satisfactory home inspection. Both of these are your "get out of jail free" cards if you should get cold feet.

If you do decide to give up the financing contingency, at least attach a letter from your lender showing you are cleared for funding, and attach a proof-of-funds statement.

But think twice about dropping the inspection clause. The house may look great to you, but it takes the trained eye of an independent home inspector to determine whether you are buying a pig in a poke. If he finds that the roof must be replaced, or there's a hidden leak in the basement, the inspection clause lets you change your mind and move on to the next house.

You might ask the seller if he had a pre-inspection done before listing the house, and ask to see it to ease any concerns you may have.

-- Beef up your earnest money. Don't just attach a $1,000 check to your offer. Bump it up to $2,500 or $5,000, or maybe even $10,000. This shows you are dead serious. It does make it more difficult for you to shop elsewhere because your cash is tied up in this house. But the money counts toward your down payment anyway, so it's no big deal if this is the place of your dreams.

-- Be their backup. If your bid comes in second, all may not be lost. Ask the seller to hang on to your offer as a backup contract. You never know what's going to happen: The other guy's deal may fall apart, and if it does, yours will rise to the top.

If you are fortunate enough to be a seller on the receiving end of multiple offers, you are not necessarily stuck choosing one offer over another. There's still room for negotiations, and you're in the driver's seat. For instance, you might inform them that you are dealing with more than one offer, and request that all wannabes come forth with their highest and best bids by a set time.

Also, realize that price may not be the determining factor. Terms also are important. If a buyer offers to pay your share of the closing costs, for example, it might seal the deal because the overall amount -- price plus closing costs -- may net you the most money. Or, if the best offer in dollar terms also requires you to replace the roof, you can defer to the next-best bid, which has no such requests.