Lured by more than 300 days of sunshine a year and "good, fun waves," Greg Leach is tapping the equity from his three-bedroom Mountain View, Calif., home to build a vacation getaway near this small Mexican resort town.

Leach, 52, who is splitting the estimated $100,000 investment with a surfing buddy, could pocket a sizable profit if he wants to. Realtors estimate that their house could fetch close to $400,000 in Baja California's sizzling market, which has shot up at least 10 to 15 percent a year for the past two years.

"Cabo has just exploded," said Leach, a building contractor.

Buyers have been snapping up homes here in the southern half of the Baja peninsula, usually in all-cash deals. Like Leach, most of the newcomers are Americans, many from California, leveraging the equity in their increasingly valuable U.S. homes.

Their purchases reflect a change in global real estate ownership: More people who are not super-rich are investing in homes abroad. In fact, some economists are starting to worry whether places such as Baja California, London and Canada's British Columbia are part of a global housing bubble driven by the same combustible mix that has fueled American home prices: low interest rates, flexible financing and sluggish stock markets that have sent investors looking for better moneymaking opportunities.

Official figures aren't kept on how many Americans are buying residential real estate abroad or how many foreigners are investing in the United States. But a survey by the National Association of Realtors revealed that 15 percent of home buyers in Florida last year were foreigners, most from Europe and Latin America. Three-quarters of those buyers said the properties were vacation homes or investments.

Economist Carl Gomez with TD Bank Financial Corp. said Americans make up as much as 10 percent of the home buyers in the British Columbia cities of Victoria and Vancouver, which have experienced double-digit-percentage price increases in recent years.

Like most buyers of homes abroad, Mike Pariseau wasn't seeking riches when he bought his first four-bedroom house in Victoria in 1996. He and his wife, who is Canadian, had been going there for vacations. That home proved to be such a good investment, though, that they bought a condominium last year where their daughter is living while attending college.

Pariseau paid about $384,000 for his Canadian properties, tapping the equity in his Santa Barbara, Calif., home, which has jumped in value from $210,000 to $1.2 million in the two decades since he purchased it.

"As far as I'm concerned, real estate is the only way to be," said Pariseau, a software consultant. "We've got some money in managed funds, but it doesn't even come close."

Although housing markets historically have been driven by local buyers and sellers, globalization -- and the Internet -- has made it easier for people in the fastest-growing markets to export their wealth.

Some economists fear that if the U.S. economy hits a rough patch, heavily indebted Americans would be forced to sell their second homes or dump investment properties, triggering price drops in the United States, as well as in places such as Baja that depend heavily on American money.

Investment bank Morgan Stanley & Co. estimated this year that property prices in two-thirds of the world were either highly inflated or moving quickly in that direction.

Some worried governments are trying to cool their housing markets in hopes of facilitating a soft landing. The Chinese government has raised taxes and tightened lending in an effort to tamp down prices that have doubled over the past two years in markets such as Shanghai. After the British and Australian governments hiked interest rates, housing prices in those markets started to slow.

But even the threat of hurricanes, restrictions on foreign investment, and soaring electricity and water bills haven't dampened America's enthusiasm for Baja. Dollars have transformed this region into an American enclave, where English is the lingua franca; the U.S. dollar is the currency of choice; and must-have accessories include a security guard, an infinity pool and high-speed Internet access.

The 20-mile stretch of coastline between the towns of Cabo San Lucas and San Jose del Cabo is a string of luxury resorts and gated residential communities with private clubs and designer golf courses. The luxury complex on Cabo San Lucas's Medano Beach sells six-week-a-year "fractional ownerships" in its two-bedroom ocean-view condominiums at prices starting at $136,000.

"It's really been a tremendous investment," said Brent Brown, 46, owner of a chain of Utah auto dealerships, who recently sold his home in Cabo San Lucas for $4.3 million, doubling his investment of two years earlier.

Investing in Mexico carries substantial risks. Real estate agents aren't regulated, and there have been several cases recently of people with millions of dollars in escrow funds that had not been deposited in legitimate accounts, according to people involved in the real estate industry.

The Mexican constitution prohibits foreigners from owning land within 30 miles of the coastline or 60 miles of the border. But the country amended its laws to encourage foreign investment after the passage of the North American Free Trade Agreement in 1994.

Now, foreigners can buy property through a bank trust known as a fideicomiso, said Mitch Creekmore, co-author of a new book called "Cashing In on a Second Home in Mexico" and a senior executive at Stewart Title Guaranty Co., the leading provider of title insurance in Baja.

Not everyone believes that a global housing bubble is about to burst. Thomas Davidoff, a realty expert at the University of California at Berkeley, said most buyers are long-term investors, not speculators, and are unlikely to resort to fire sales or default on their loans even if the economy slows.

"There are definitely some idiots . . . out there," he said. "But are those guys setting prices, or are they a small part of the market just trying to get rich?"

James A. Fetgatter, chief executive of the District-based Association of Foreign Investors in Real Estate, argues that foreign investors can be a stabilizing force because they are usually wealthy individuals or large institutions that are less vulnerable to price shocks in any one market.

In the 1990s, however, Japanese investors, armed with a strong yen, dumped billions of dollars into Manhattan penthouses, Los Angeles office towers and swanky U.S. golf courses. When Japan's real estate bubble popped, sending the Japanese economy into a decade-long recession, many investors were forced to liquidate those properties for huge losses.

The Baja peninsula had its own scare after the terrorist attacks on Sept. 11, 2001. Americans pulled back from traveling overseas, and the real estate market ground to a halt. Housing prices started falling as anxious homeowners tried to bail out.

Chris Snell, 44, president of Snell Real Estate, which handles 80 percent of southern Baja's luxury properties, bought out his nervous partners. "I was in so deep I couldn't get out," he said.

His gamble paid off. Snell said his company has handled $270 million in sales since January, up from $120 million for all of last year.

Snell says he isn't worried about a housing bubble here.

"When I go to Santa Barbara and I go to Napa and I see people wanting to buy homes with zero percent down, that scares me," said Snell, who recently sold his own 3,200-square-foot Baja home for more than $3 million. "That is a bubble I see that can burst. When I see them coming to Cabo and buying homes with all cash and they're involved in the deal, that doesn't scare me."

Chris Snell, owner of Snell Real Estate in Baja California, says he doesn't see the Mexican resort area's recent housing boom as a bubble.