When it comes to vacation nightmares, renting a home or apartment from a scammer has to be near the top of the list. And unfortunately, there are plenty of victims who can attest to that.

"This is an epidemic problem, and it's destroying people's vacations," said David Quinlan with the Better Business Bureau of Alaska, Oregon and Western Washington.

Online classifieds are a favorite place for scammers to play their tricks and target their victims. They often hijack the listings for legitimate rental properties and make themselves the contact person. Their goal is to get you to pay the full rental or at least a sizeable security deposit upfront.

"We've seen horror stories where people wired the money, thousands of dollars, got some bogus keys, showed up and the rental property wasn't there—it didn't even exist," Quinlan told me. "Just put yourself in their position. It makes your stomach turn."

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Earl and Barbara Renken, who live near Sacramento, California, got burned a few years ago. They had gone online and found a summer rental apartment in Anchorage, Alaska, at a low price. They corresponded with the sales agent for the rental company who was so accommodating, he even asked them what color they wanted him to repaint the place. The Renkens' son, who lives in Alaska, drove by the property and said it looked good.

When they arrived in Anchorage, they discovered that they'd been duped. They had paid almost $1,500 to an online swindler. The landlord told the Renkens the place wasn't for rent and hadn't been advertised.

"I was really ticked off," Barbara remembered.

Earl contacted his credit card company and the charges were reversed. Luckily, they had a friend in town who let them spend the summer for free in his basement apartment.

"If we'd been strangers in town, just wanting to summer in Alaska, we would have been up the creek," Earl told CNBC. "After paying for this place, we couldn't have afforded to pay for another, so I don't know what we would have done."

Rental scams can happen anywhere, but properties in popular vacation destinations, such as Florida, are a favorite target.

In Cape Coral—just south of Fort Myers—the police department has 20 active vacation rental scam cases. Some of the victims who've fallen for these bogus ads have lost several thousand dollars.

"Once that wire transfer is completed, it's almost impossible for us to track it down," said Detective Sgt. Dana Coston. "In most of these cases, the price that was offered was very far outside the market norm, and that should be a red flag."

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