The Nov. 30 deadline for first-time home buyers to qualify for a federal tax credit means deals need to be inked soon to make it through the closing process on time.

"If you're not in contract within the next 30 days, your chances are pretty slim," said Dan Rider, a broker with Dickson Realty in Reno, Nev. The looming deadline has some "getting twitchy" and putting in multiple offers to be sure one sticks.

But this frenzy reminiscent of the housing boom could be short-lived. While the market appears to be recovering from its worst downturn in decades, the expiration will help show if the recent improvement is permanent or a mirage.

Several congressional proposals to expand and extend the credit have been introduced, while the industry is lobbying fiercely. The National Association of Home Builders plans a print- and radio-advertising campaign in coming weeks. But with a multibillion-dollar price tag possible to keep the credit going, success isn't guaranteed.

Some economists and housing analysts fear the credit offer only encouraged more housing supply and pulled deals forward and that its absence will push the market back into the doldrums, with weakness stretching into next year. Extending it would remove the pressure to buy now.

"You have to have a deadline," said Christopher Thornberg, a principal with Beacon Economics, a Los Angeles-based research firm. "The fact that this program is ending is exactly what's necessary for the program to work."

The government engineered the credit to salvage a market nearly paralyzed after home values plunged and jittery buyers were stuck on the sidelines. For deals done between Jan. 1 and Nov. 30, first-time buyers — defined as those who haven't owned a principal residence in the past three years — can claim 10 percent of the home's purchase price, as much as $8,000. Single taxpayers making as much as $75,000 and married couples earning as much as $150,000 qualify for the full tax credit.

Buyers appear to be stirring: Moody's Economy.com chief economist Mark Zandi estimates the tax break will ultimately spur almost 400,000 additional new and existing sales.

Pending home sales have surged for six straight months — whittling what had become a bloated inventory, particularly for cheaper homes. With supply levels of units priced below $100,000 dipping to an anemic two months in the West, "we have heard complaints of not enough lower-priced inventory," said Walter Molony, spokesman for the National Association of Realtors.

But with the extension not guaranteed — and the possibility of a gap should it expire before a revamped program is initiated — builders and real-estate agents aim to squeeze in as many deals as possible. They are urging buyers to schedule closings early to ensure that last-minute problems don't push the closing into December.

"It would be really sad, and it would be devastating, for a first-time buyer to get to the closing table…and have something messed up either with their appraisal or their financing," said Jerry Howard, the builder group's president and chief executive. "You miss the credit."

Another hurdle is the calendar: Nov. 30 is the Monday after Thanksgiving weekend, so many deals could have to be wrapped up by Nov. 25, the day before the holiday.

Because the permitting process and construction typically takes several months, many new home builders are no longer guaranteeing new construction will be done in time to qualify. Some say that is derailing potential sales.

To keep deals coming, builders are steering buyers to homes already built or those near completion, known as specs, that can close more quickly.

By Dawn Wotapka, www.dowjones.com