(MONEY Magazine) – By the time Bill and Mary Barbour retired to Florida in 1983, they were already well-seasoned travelers. The couple had stayed in lavish hotels throughout Europe and the Far East during Bill's frequent business trips as a publishing executive. But after reading a newspaper article about home exchanges, the couple decided to see the world in a different way--by trading homes with families who live in places they wanted to visit. In the past 12 years Bill, 74, and Mary, 72, have swapped their two-bedroom luxury condo in Sanibel Island 80 times for different houses around the world. They reckon that home swapping has saved them a grand total of $151,200 over vacationing in hotels.

Each year as many as 200,000 people, most of them folks over 50 like the Barbours, trade living quarters and vacation in the homes of strangers for anywhere from a week to several months. The savings over conventional traveling are impressive, because the accommodations are free. According to the survey the Barbours did for their book Home Exchange Vacationing (Rutledge Hill, $14.95), three out of four home exchanges come with a car as well. Consider that a week for two in London with outlays for modest hotels, meals, and car rental would almost surely total more than $3,000, while a similar vacation with a home swap would cost only about $600. That sort of value makes swapping almost irresistible.

Almost.

"If you aren't into adventure as well as saving money, you shouldn't do it," says Lori Horne, 52, the current co-owner of Intervac U.S., a home-exchange service that has been in business for 42 years. She cautions that "the best candidates for exchanging are people who want the experience of having neighbors and friends in the places they're visiting." And the people who can calmly bear the thought that strangers will be staying in their home. Fortunately, swapping usually draws very responsible travelers who give your quarters the care they hope you are giving theirs.

Most experienced swappers use one of the many home-exchange services (see the box below). For a small fee that ranges from $40 to $80, you'll be listed in one of several service directories published throughout the year. You'll receive several of them, however. The listings, organized geographically, describe and sometimes picture the houses. After each entry are the owner's name and address and the countries he or she wishes to visit.

Hawaii, California, Florida and cities like New York and Boston are the most popular destinations, but don't give up if your home is located in a less glamorous spot. Last year Alan Burley, a 48-year-old school counselor, and his wife Rachel, 44, a speech pathologist, listed their Libby, Mont. home with HomeLink, hoping to trade it for a beachfront house somewhere in the South. But the couple feared Libby's four-hour drive from the Spokane airport might outweigh its location on the banks of the picturesque Kootenai River. Nonetheless, within two months their exchange drew three offers, and they accepted one for 10 days in late July and August from a woman who owned what Alan describes as a "terrific" house on the water in Holden Beach, N.C.

If you want to list with a service, you should do so at least six months before you plan to go away. The directories require information about two months in advance of the publication date, and then you'll need to get in touch with owners and make arrangements. While you're waiting for the directories, compose the letter that will sell your casa and its locale to someone you want to swap with. Highlight your proximity to cities, local sightseeing attractions and recreation areas. And if you are adamant about no smoking in your home or car, or no pets, say so up front. When you receive the directory, send your letter to owners of places you like along with photos of your house. How many letters should you send? The Burleys sent out 25 to homeowners in the South describing the attractions of rafting, fishing and hiking along the Kootenai and the plesures of an evening spent in a glass-enclosed lookout tower on Big Creek Baldy mountain about 20 miles away.

To vet candidates whose home you're interested in, interview swappers who have previously exchanged with them. If they check out, then nail down the specifics in an informal letter of agreement. It should spell out, among other things, the dates of the exchange--the Barbours describe a swap that almost went awry when the British family thought 4/11/96 meant the house was available Nov. 4, instead of April 11 as their American counterparts intended--the number of guests who will be staying in the house, who is permitted to use the family car, who mows the lawn, and who is responsible for paying for home repairs and long-distance telephone calls. Read your auto insurance and homeowners policies to be sure your guests are covered.

To minimize problems while you're away, leave detailed information about your house, describing how to operate appliances and where to find essentials such as the fuse box. You might also mention any quirks. Maggie Hanusa, 64, who has exchanged her home in Wailuku, Hawaii 28 times in the past dozen years, leaves instructions in a loose-leaf binder in the kitchen, taking special care to alert her guests to the "lovable, small pets" who share the house--little lizards called geckos. "We Hawaiians have learned to live with geckos, since they are harmless," she says. "But they can't be house-trained, so you have to clean up after them a little."

Veteran swappers say you'll probably want to start thinking about your next exchange almost as soon as you return from your first. With a little planning, flexibility and luck, you could find yourself vacationing in some surprising places. "When our older son married a girl from a small town in South Dakota, we arranged an exchange so I could make the wedding cake," Maggie Hanusa, a prizewinning baker, recalls. "The couple who answered our ad discovered they could get a Hawaiian vacation for basically the cost of air fare." And no extra charge for the geckos.