The tax credit is so important to some buyers that they are adding a clause to their contracts, allowing them to back out if the sale doesn't close by Nov. 30.
While home sales and housing construction have risen steadily after hitting bottom earlier this year, most economists believe that the worst isn't over for home values.
In August, the median price was $177,700, down from the peak of $230,300 in July 2006, but still above the bottom of $164,800 in January, according to the Realtors group.
Prices could see a double dip because rising unemployment is having a ripple effect on foreclosures. The jobless rate, currently at 9.8 percent is expected to rise as high as 10.5 percent next year, causing more people to be unable to afford their monthly mortgage payment.
"There's more supply that's going to come into the marketplace," said Stan Humphries, chief economist at real estate Web site Zillow.com. "That additional supply will outpace demand."
Some signs of softer prices may already be appearing. A government index released Thursday showed U.S. home prices dipped 0.3 percent from July to August.
That drop "supports our view that the housing recovery will be slow and bumpy," wrote Paul Dales, U.S. economist with Capital Economics.
With concerns about the housing market still prominent, Congress is considering several proposals to extend the tax credit for first-time buyers.
Senators Johnny Isakson, R-Ga., and Christopher Dodd, D-Conn., want to extend it through June 30, and expand it to include all home buyers, at an estimated cost of $16.7 billion. One potential roadblock, however, emerged this week. There are concerns that some of the 1.5 million applications for the tax credit are fraudulent.
At a hearing before a House subcommittee Thursday, J. Russell George, the Treasury Department's inspector general for taxes, questioned the legitimacy of some 100,000 claims for the credit, potentially including some illegal immigrants and 580 people under 18.
The youngest taxpayers to apply for the credit were 4 years old, his office said.
While the program has widespread support in Congress, there are growing concerns about the costs.
The cause, said Sen. Jack Reed, D-R.I., "is a worthy one." But "I hope we can find ways to pay for it."
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