Timeshare buyers are cautioned about labeling their weeks as “investments.” Think of it as prepaid vacations, timeshare developers famously say.

While an investment, especially in real estate, often stands an excellent chance of making money, the usual return on a timeshare typically centers on enjoyment rather than cash.

Timeshares continue to be big business — more than $8 billion a year — despite the sluggish economy. The American Resort Development Association reports that more than 4.5 million U.S. households own one or more timeshares in 1,604 resorts.

A growing number of entrepreneurs, with an exceptional grasp on how to purchase, close and sell timeshares have begun to acquire inexpensive weeks at upscale resorts via resale channels. They then rent out the properties at a weekly or a per-night rate comparable to what a nice hotel would charge.

“We have people who will go to our Web site and buy 10 weeks at a time,” said John Locher, vice president of sales and marketing for Redweek.com, an online conduit for timeshare buyers, sellers, landlords and renters. “They have studied certain resorts and markets and know what’s possible as far as rental income during a majority of the year.”

Steve Shermoen, a self-described “small-town attorney” from International Falls, Minn., said he now controls about 100 timeshare weeks and plans to spend most of his retirement years rotating through some of them in different parts of the world. Is he concerned about owning so many pieces of the only real estate asset class that always loses money when resold?

“You cannot make the rental concept work if you buy directly from the developer,” Shermoen said. “You have to be sure of what you are buying and purchase only on the resale market. The cost from the developer simply is too high for it to become a rental that will pencil out.”

Shermoen and others like him typically stick to Marriott, Hyatt, Hilton and other upper level properties that they can pick up at a fraction of the original purchase price. They often seek sellers who are extremely eager, often desperate, to dump a timeshare contract because of unexpected circumstances including loss of job, divorce or death. Many timeshare bargains can be found online right after the annual fees are announced for the coming year. As an attorney, Shermoen also offers to close the transaction at a discounted fee.

“Many people are grateful that there is a buyer who is willing to take the week off their hands,” Shermoen said. “They simply are tired of paying the annual fee and can’t wait to get out from under it.”

I was one of them, yet I didn’t even consider renting it out. Nearly 20 years ago, I spent hundreds of dollars marketing the timeshare and considered myself extremely fortunate to get back most of my investment. While some people swear it’s the only way to travel with a family and that the international “bank” of resorts not only offers flexibility but also destinations they normally would not consider, it didn’t happen for us. Basketball tournaments, family reunions, budget restraints and four different school schedules, coupled with the fact that we are very picky about accommodations, led to a three-year timeshare shutout. We owned the “points” for three years and never spent one night in a timeshare resort.

Timeshares come in a variety of packages, including a points program where owners exchange a specific number of accumulated points for a week, weekend or individual nights at resorts that participate in the points arrangement. Some of the larger timeshare companies now offer a point system, permitting owners to split the traditional week into smaller segments. The concept has worked very well for out-of-town family reunions, weddings or simply a needed weekend getaway.

The idea of breaking up the timeshare week into a few one-or-two night stays can also make sense for vacationers traveling a country by car. The average worker typically receives two or three vacation weeks each year and often prefers not to spend a large percentage of that time in one location.

The value of the points can vary greatly. For example, weekend nights will require more points than weeknight stays, and popular resorts will demand more points than a run-of-the-mill getaway. In addition, the future value of points also can be a consideration — not unlike trying to predict the future value of money.

Similar to dollars, timeshare points can be worth a lot more today than they will be down the road. If a resort continues to increase the number of points necessary to rent the unit you covet, the value of your allotted points will decrease. You will need more annual points than the number you are receiving now to reserve the same unit. Seniors and other consumers on fixed incomes may not be getting the perpetual week they initially purchased, which could seriously curtail their dream vacations down the road.

Properly applying points and a resort’s bonus time are just two pieces to successfully renting timeshares. There’s also a huge caveat when shopping.

“Some people try to sell you weeks they don’t really own,” Shermoen said. “It’s another one of the pitfalls to consider when buying and selling. Acquiring and renting out timeshares is complicated and not for the unwary. If you are going to jump in, you have to do your homework.”

Tom Kelly is a Seattle area writer who covers real estate issues.