What does all this mean to buyers and sellers? In short, says one agent, forget what you thought you knew about real estate.

For buyers

Consider whether and where to leap. For buyers, the changing market may mean it's time to think about buying if homeownership previously was too costly. "Yes, there are affordability problems in California, the Southwest and Florida," says PMI's Milner. "But there are also huge swaths of the country where housing is still very affordable, and in some cases more affordable (in percentage of income spent on housing) than it was 10 years ago." The most affordable regions are the South and Midwest. Just be certain you can weather the storm if home values drop after you buy.

Realize it's a home, not a cash machine. Think of your home as a place to live, not as a way to make quick money. "Instead of a stock, which is just a piece of paper, you get to consume shelter," says Milner. Your home probably will appreciate, but slowly. Historically, homes appreciate at a rate of about 4% to 6% a year, on average, over any given 10-year period, he says.

Choose a mortgage by interest rate, not payment amount. Proceed cautiously when shopping for a mortgage. Consider a traditional fixed-rate loan so you'll know exactly what your payment will be for the entire life of the loan. You may find adjustable-rate mortgages (ARM) with lower payments that later adjust up, but don't gamble that you can make a higher payment when the introductory period is over or when interest rates rise, as they are likely to do.

Don't bet on house appreciation. Don't make financial plans or take on debts that bank on the near-term rising value of real estate. In the post-bubble world, the risk to your financial stability is just too great. A number of the 176,137 foreclosures filed in May -- a 90% increase from last year at this time, according to RealtyTrac -- were by borrowers who'd gambled they could refinance a risky mortgage once their home had appreciated. Buyers "are going to need to be very prudent because they are not going to be bailed out by an appreciating home," says Milner.

For sellers Sweeten a sale by helping a buyer with closing costs. Potential buyers may be sitting on the sidelines because, although they can make monthly payments, they haven't got a down payment saved up, says Steven Schafer, an agent with Boca Executive Realty in Boca Raton, Fla., one of the riskiest markets identified by the PMI study. Consider contributing up to 3% of closing costs. (Just be aware that states and lenders often limit seller contributions.)

Exploit the Internet. Open houses, while still an important sales tool, are being eclipsed by the Internet. Buyers now use Web research to learn what's for sale locally before stepping a foot out of their homes. With scads of homes on the market, you must figure out how to distinguish your home from others like it on the Internet. Schafer and Thompson, the Phoenix-area agents, create a Web site for each house they represent, usually using the home's address as the site address. If your agent can't register the link for you, do it yourself. You can also set up a Web page yourself with a modicum of computer skills or pay a Web site creation company to do it for around $30, says Schafer.

Load your listing with pictures. Schafer advises "visually communicating" with buyers by choosing an agent with an outstanding Web site and contributing plenty of great photos of the house.

Use a "virtual" tour. Sophisticated real-estate sites use panoramic photo features or streaming video so buyers can get a 360-degree view of the property from a single vantage. With virtual tours, buyers in other states and other countries can get a good feel for your home without actually stepping foot inside.