If you think retirement living means selling the old homestead and moving to a smaller place in a warm climate, think again. A new study shows that baby boomers — the oldest of whom turn 57 this year — continue to rewrite the rules.

One-fourth of homebuyers age 50 and older are paying more for their retirement homes than for their previous houses, according to a new study by the National Association of Home Builders and Countrywide Home Loans. Three-fourths of buyers 50 and older are searching for homes in developments that provide yard or grounds service and exterior home maintenance, leaving them more time for leisure, travel and socializing. Most buyers prefer a location close to their current home.

The survey results help explain why the United States is in the midst of a senior housing boom. You don't have to look far to find a community where admission is targeted to households in which at least one person is 55 or older.

Unlike the massive Sun City retirement towns that sprawled across the desert of Arizona 40 years ago, these are small, often high-end gated enclaves with clubhouses and fitness centers tucked into existing communities. Another difference: Today's "active adult" communities are sprouting up all over the country, even in such four-season locations as Colorado, Illinois, Massachusetts, Pennsylvania and New Jersey.

By 2005, one in four Americans will be 55 or older, making them the fastest-growing consumer market — a fact not lost on homebuilders. And the homes themselves have improved, boasting high-end amenities such as gourmet kitchens with granite countertops, entertainment rooms to house big-screen TVs and home offices with high-speed Internet connections.

"People are seeing more of these properties and realizing they are not just for geezers," says Margaret Wylde, president of the ProMatura Group, a research firm that specializes in the mature market. "They attract people who want an active lifestyle."

For example, a New Jersey couple retiring this year recently bought a two-story, 2,800-square-foot house for $400,000 — about what they expect to get for their current home. Although they liked the idea of an elegant single-family home where someone else mows the lawn and shovels the snow, what really impressed them was the instant sense of community. The developer organized a dance so that everyone who had signed a contract for a new home could meet one another. The community also has a book club and a fitness center.