ORLANDO, Fla. -

Do you have thousands of frequent flyer miles or credit card points you're wondering what to do with?

[WEB EXTRA: Buy and sell points here and here]

Turns out people are making hundreds to thousands by selling them to third party brokers.

Carlyn, who prefers we only use her first name, is one of those travelers. With a busy travel schedule and a points earning credit card, she racked up thousands of airline miles with no plans to use them.

She was enticed by online ads offering money for her unused miles or points.

"I didn't see the value in holding onto them hoping that I would find a flight I could use them," she says. 

She made more than $450 by selling her 57,000 miles.

Though Carlyn made a nice profit, experts say each time you sell your airline miles or points - you're taking a gamble.

Brian Kelly, founder of The Points Guy.Com, shares his travel insight with readers worldwide via his website. He says it's become big business but there are risks involved.

If you check the fine print of many reward programs, you'll find selling your miles or points is not allowed and if you get caught, you could lose all your miles or points, have your account cancelled and be banned from the program.

"You're not going to end up in a jail cell but the airlines are pretty clear and they play hardball with people who sell their miles and points."

When people sell miles or points, brokers redeem them for an airline ticket they sell to someone else.

And while in some cases it's permitted to transfer points or miles to family or friends, experts warn the industry is watching for transfers and tickets that seem unlikely.

"The airlines and credit card companies are looking for transferring of points to people in different states, different last names in different geographical regions."

Eli Hoffman runs flipmymiles.com, one of many mileage brokerage firms we found operating online. He acknowledges the risks but says over the last several years his company has sold more than three billion miles and points.

"The airlines definitely don't want the client to sell their miles to a company like ours," he says.

"Even if something did arise, we still guarantee payment," Hoffman continues, "you would keep the payment even if your account got shut down."

And while Flip My Miles says they guarantee payment, experts warn that there are some fly-by-night companies buying and selling miles and points.

"If you sell your miles to a company, they take them all and they don't pay you, you can't really go to the airline and say 'hey I sold my miles and this guy didn't follow through on his payment."

Flip My Miles says the going rate for frequent flier miles is about one-cent per mile.

So if you sold 100,000 miles, you'd make about a thousand dollars.

They say selling points is even more lucrative. They're worth about 1.3-cents per point.

As for Carlyn, she got an email from the company telling her that her points helped another customer book a flight to Paris.

"I made money selling miles that I'm no longer using and somebody else that needed a last minute flight was able to save money," she said.