Congress delivered an early Christmas present to the real-estate industry yesterday, extending and expanding a popular tax-credit program for home buyers that some say has helped prop up the housing market here and elsewhere.

Local real estate agents said the congressional action could lead to a busier-than-normal winter for home sales in Massachusetts - and then a very busy surge early next spring as home buyers try to beat the new deadline for the credit program’s expiration.

“I know it sounds self-serving, but I truly see this as a great stimulus (for the economy),” said Gary Rogers, president of the Massachusetts Association of Realtors and a broker with ReMax First Realty in Waltham.

The current $8,000 tax credit for first-time home buyers was due to expire at the end of this month.

Yesterday, the House, following Senate action Wednesday night, overwhelmingly approved the extension of that credit program until next April 30, when sale contracts must be signed in order to qualify for the credit. Home buyers will have until June 30, 2010 to close on deals.

But Congress added some extra goodies in the package that will benefit many more potential home buyers.

Those who have lived in a home for five years or more can now qualify for a $6,500 credit if they purchase a new home, allowing people to “trade up” for a bigger house or buy a smaller abode.

Congress also expanded the income eligibilty requirements - from $75,000 to $125,000 for individuals and $150,000 to $225,000 for couples.

Nicolas Retsinas, director of Harvard’s Joint Center for Housing Studies, said the nation’s housing market is now on “government life support,” so it’s important that the credit program was extended until next spring.

But he said that, sooner or later, the housing market has to stand on its own two feet.

“Tax credits borrow demand from the future,” he said. “At some point, the government has to exit the subsidies business.”