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.

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.