Trying to save money by sharing a vacation residence can end up costing more then you bargained for, according to Susan Budowski, an attorney who specializes in timeshares.

Advisors who have clients considering the purchase of a vacation timeshare should know that most time-shares are sold in perpetuity, like a home sale, and the resale value is often quite low, says Budowski, who is based in Venice, Fla.

What buyers sometimes forget is that maintenance fees will be charged every year, even after the purchase loan is paid, and the fees will increase over time, she says.

To help determine the real cost of ownership over a five-, 10-, 20- or 30-year time spans, Budowski has developed a free calculator available on her website, SusanBudowski.com. To determine the cost over time, the potential buyer puts the purchase price and annual fees into the formula and it determines the long-run cost, including increases in annual fees.

“I don’t like to see people lied to, and a lot of the time-share pitches do not tell the true cost of ownership,” she says. “Annual maintenance fees are killing people. A lot of people have difficulty reselling their shares. There are listings for time-shares for $1 on eBay by people who just want to get out of the maintenance fees.”

Special assessments also can be levied if the units are damaged in a hurricane or other natural disaster. When the timeshare owner dies, the unit is inherited by the heirs who may or may not want it.

“I created the calculator to be simple to use. It also shows what the monthly maintenance fees will be in subsequent years based on average, industry-wide increases,” she says.