Overleveraged sellers. Owners who owe up to or beyond their current home value are in a dicey situation, but only if they have to sell, says Gaylord. "If they can hold on awhile, that value will come back," he says.

Homeowners who can't afford their mortgages. Many are left stretching to make payments or trying to sell the home for more than the market will bear. Help is available. Some homeowners will qualify for relief under the Obama administration's relief program. Or, try to work out an arrangement with your lender or loan servicer, either on your own or with the help of a housing counselor. Find a HUD-certified counselor on their Web site or call (800) 569-4287. You can also locate a housing counselor through the National Foundation for Credit Counseling. If you're a veteran or it's a VA loan, contact the U.S. Department of Veterans Affairs at (877) 827-3702.

Sellers who bought at inflated prices. "If you bought your house last year or in 2005 with a low down-payment mortgage, this is a terrible time to be selling," says Zigas.

Homes and neighborhoods losing to foreclosure. In a normal market, there are 150,000 to 160,000 bank repossessions nationally every year, says Rick Sharga, senior vice president of RealtyTrac, which publishes foreclosure data. Right now, the market is seeing half that number every month, he says.

Builders. In an average year, builders start construction on 1.3 million single-family homes nationwide, says Robert Denk, assistant vice president for forecasting and analysis for the National Association of Home Builders. In 2008, only 617,000 starts were reported.

Sellers in bad markets. "Any seller who is being forced to sell in a declining market is losing big time," says Zigas. "Particularly recent buyers."

Owners who want to refinance in a hurry. "It's a little more difficult today," says Gaylord. "Appraisals are more stringent." Shop around and allow plenty of time to get it done (everybody has the same bright idea). If the initial answer is "no," keep shopping.

People who buy for price instead of value. "A low price doesn't make it a good investment," Kiyosaki says. Look at the whole package.

Buyers and sellers waiting for approval in a short sale. "A lot of buyers think short sales are the way to go," says Phipps. The idea is to get a homeowner out from under a loan that's higher than the house value and give the buyer a market-priced deal. But real estate agents and industry watchers have noticed that the transactions often drag out for months, frustrating buyers and sellers. "It's not an efficient process," says Phipps.

Foreclosure buyers who don't do their homework. With many foreclosures, the sale really is "as is," says Phipps. That means you have to live with (or correct) any flaws you find. "It's not always as good an opportunity as you think," he says. A safe bet is to have an inspection done before you buy.