NEW YORK (CNNMoney.com) -- If you're thinking of buying a home, there could be a big bonus for you in the economic stimulus bill that's now before Congress.

Among its many provisions is a $7,500 tax credit for first time home buyers. The House passed the $819 billion stimulus plan, including this tax credit, in a vote late Wednesday. The Senate may vote on its version of the bill some time next week.

Technically, the stimulus bill is actually changing the terms of the $7,500 tax credit that was issued as a part of the Housing Recovery Act, which Congress passed last summer. That legislation required that the tax credit be repaid over 15 years, making it more of a no-interest loan. Not surprisingly, the measure had little impact on the market. The stimulus bill now under consideration would make that tax credit a true credit that doesn't need to be repaid.

Many in the housing industry believe this credit could do a lot to jump start the moribund housing market.

"Our economists have studied the effect [of the credit] and they say there could be a 10% increase in home sales if it's implemented," said Mary Trupo, a spokeswoman for the National Association of Realtors. "It gives people who are sitting on the fence or who have inadequate funds for closing costs an incentive to act now."

A 10% increase would yield an extra half million sales this year.

Who qualifies

To be eligible, buyers cannot have owned a home for the past three years, and the new home has to be used as a primary residence. The credit phases out as income rises above $75,000 for singles and $150,000 for couples, and disappears entirely at $95,000 and $170,000, respectively.

Applying for it is easy, or at least as easy as doing your income taxes. Just claim it on your return. That's it. No other forms or papers have to be filed.

Both the Senate and the House versions of the new act remove the requirement that buyers repay the credit. The Senate bill applies retroactively to any purchase completed between January 1, 2009 and the end of August. The House version is also retroactive to the start of the year, and expires at the end of June. As long as buyers don't sell for at least 36 months, they keep the money.

And the credit is refundable, meaning that it can be claimed even if the amount of the credit earned exceeds the buyer's tax liability. So even if your total tax bill comes to just $5,000, you can still qualify for a full $7,500 refund.

The housing industry has been pushing this idea for many months, arguing that first-time homebuyers are the key to boosting home sales. First time buyers who purchase from existing homeowners free those sellers to trade up to bigger, better houses.

Buyers beware

But the credit has its drawbacks, according to Bob Williams, a spokesman for the Tax Policy Center, which gave it a mediocre C+ grade in its Tax Stimulus Report Card.

Williams argues that the credit is poorly targeted because it goes to every first-time buyer, not just the ones who wouldn't buy without it. So, it merely provides a windfall for many people who would have purchased anyway. (See correction, below).

And in the end, a $7,500 tax credit, regardless of the details, does nothing to address the issue that's holding most buyers back - the suspicion that prices are going to keep falling.

"As long as people are uncertain about what markets are going to do, this won't help much," said Williams. "It's not enough to change that."

The industry would like to make the tax credit stronger by making it available to all homebuyers, not just first-timers. And it's pushing to have the credit last through the end of the year, at least.

"By the time it's implemented," said Trupo, "there could be very few months left to act."

An earlier version of this story incorrectly stated that the tax credit for a home purchased in 2009 could only be taken off of 2009 taxes. However, homebuyers can choose to take the credit for 2008, according to the IRS. Even if they buy a home after they've filed their 2008 taxes, they can file an amended return.