PLANO – For Alfredo Márquez, a plumber in Richardson and an illegal immigrant, the decision to buy a home in North Texas was easy.

"After a while you realize that you're here for a long time, and you don't want to throw your money away by renting," said Mr. Márquez, who also owns a home in his hometown in Mexico, San José Iturbide. "It's a way to set roots and invest in the future."

North Texas is attractive for immigrants such as Mr. Márquez because homes are affordable here – even if you're an illegal immigrant with working-class wages.

"New rules and affordable home prices in Texas are leading to an increased number of illegal immigrants buying homes in North Texas," said Marty Martinez, a North Texas real estate agent and board member of the Washington-based National Association of Hispanic Real Estate Professionals, or NAHREP. "Texas real estate prices provide a big incentive. First-time homebuyers can generally buy a home for under $100,000."

While it's illegal to hire undocumented workers, there's nothing wrong with lending them money. In fact, federal and state governments are subtly encouraging banks to issue home mortgages to illegal immigrants through little-known individual tax numbers. Banks are also training employees to speak Spanish and guide customers into homeownership.

Foreigners who are not eligible for Social Security cards can apply to the IRS for an individual tax identification number, known as ITINs, which enable them to pay taxes. About 8 million ITINs have been issued since 1997, and an ITIN can be an illegal immigrant's ticket to a home mortgage.

Immigration and mortgage specialists say it's difficult to get firm figures on the number of homes purchased using ITINs. This is partially due to privacy concerns. Other illegal immigrants, including Mr. Marquez, instead will purchase a home through a relative or trusted friend who is in the U.S. legally.

"Regardless of the varying opinions about the federal government's immigration policies, the bottom line is simple: The majority of these individuals are most likely not going to be deported," said Rick Troutman, president and CEO of Hispanic Lending.Com, a Dallas-based group that specializes in lending money to Hispanics. "They all need a place to live."

Mr. Troutman estimates that as many as 105,000 illegal immigrants live in Dallas County alone, plus tens of thousands more throughout North Texas. And with home prices relatively low in North Texas – compared with other places favored by immigrants such as Los Angeles, Chicago or Miami – Mr. Troutman believes many of them are potential buyers.

In 2004, NAHREP published a study that estimated that more than 200,000 illegal immigrants from Latin America qualify to buy homes. They represent a housing mortgage market of about $44 billion and growing, said Frances Martinez Myers, NAHREP president. Mr. Troutman calls that figure conservative, saying the actual numbers are multiples of that.

Either way, said Ms. Martinez, legal residency "has never been a condition to purchase a home. Being in the country legally or not is not an issue when you are buying a house."

As the U.S. housing market slows down, Mr. Troutman says, real estate companies and banks are looking at the nontraditional homebuyer, and the immigrant population represents a booming market.

"The numbers are too large to look the other way," Mr. Troutman said. "Also, the default rate for Hispanic mortgages is very, very low."

He estimates that the default rate for those who buy homes using ITINs is less than 1 percent. The default rate for the general population is 3.7 percent.

Ironically, the U.S. government's restrictive immigration policy provides an added incentive to buy homes for many immigrants. In the past, immigrants traveled back and forth across the border to visit relatives and to stay in touch with their homeland. But as crossing the border has become more difficult, dangerous and expensive, more immigrants are putting down roots in the U.S., despite their illegal status.

That trend has led to a backlash in the United States, as some localities have enacted measures to discourage illegal immigrants from taking up residence. This month, Farmers Branch passed ordinances making English the official language and approving fines for landlords who rent to illegal immigrants. Police officers are being empowered to check residency status of those arrested for crimes.

Mr. Márquez, the Richardson plumber, said he has seen his home in San José Iturbide only once since 2002. It's a brick home that would not look out of place in Plano.

The Christmas holidays usually get the better of Mr. Márquez. He aches for home, family and friends, and says he usually makes a vow to his loved ones in Guanajuato state that "next year" he will return for good. But demand for his plumbing expertise keeps him here.

"Every year is a year of broken promises," he said. "I never seem to be able to return home, so that's why having two homes makes sense."

Staff writer Dianne Solís contributed to this article in Dallas.