"As we've worked with a lot of different leasing companies, we've learned what they look for, so we put together a process that will get most buyers with good credit approved," says Sergio Stiberman, CEO and founder of Leasetrader.com.

"But because it is harder to get approved to lease a vehicle than buy one, in some cases preapproved buyers aren't ultimately approved by the leasing company," he says.

Buyers need to be prequalified, so they will pay a fee for a credit check. Would-be buyers without good credit are usually out of luck. In most cases, consumers who are prequalified through the lease-trading companies are qualified by the car companies to assume a lease, but in some deals, that isn't the case.