For many consumers, the payday loan ends up as a debt trap.

Take a legitimate 14-day advance for $100. If the fee on that advance is $15, the Federal Trade Commission notes, the consumer's cost is comparable to an annual interest rate of 391 percent on a short-term loan.

Under federal law, payday lenders must disclose the cost of the loan. Federal law also requires that payday lenders cannot charge more than 36 percent annual interest to active-duty military members and their families.

But consumers who are trying to make ends meet by turning to a two-week cash advance on their paychecks must be careful. Some states have tighter regulations than others. And the industry in general has fought to exempt itself from a proposed consumer protection agency that President Barack Obama is backing.

Typically, consumers walk into a payday lending outlet and hand over a personal check for the amount borrowed plus the finance charge. The borrower receives money but the check is not cashed until the borrower's next payday. Last year, the median payday loan was for $350, according to research by the Center for Responsible Lending.

Yet the price can turn out to be far higher, especially for consumers who borrow from an online payday lender.

When William Lee took out a $250 payday loan through an online outfit, he figured he'd have to pay back $280, the money he received plus interest or fees. Lee was shocked to learn he owed $400. "For a $250 loan, you're charging me $150?" asked Lee, 48, a Detroit resident.

Cash-strapped consumers nationwide may be tempted by online lenders who offer to deliver as much as $1,500 in as little as an hour. But be warned: They can charge stunning amounts, and some consumers say their lenders even made threats to collect the money.

In April, the FTC charged a payday loan operation with illegally trying to garnishee the wages of borrowers and using other outlawed debt-collection practices.

According to the FTC complaint, Ecash and GeteCash offered loans of up to $1,000 to be repaid from a borrower's upcoming paycheck.

But the consumers often did not see terms in the online application that included a statement that wages would be garnisheed to cover delinquencies.

Borrowers were required to check a box indicating they agreed with loan terms.

The FTC charged that the online company's statement was an attempt to get around federal requirements, including a debtor's right to revoke a garnishee agreement.

The Better Business Bureau is also warning consumers that some online payday lenders have created financial nightmares for borrowers.