A photograph of a suburban house appears on the large dual screens in Charleston County's expansive meeting room, and about 125 bidders and observers get ready for the auction.

The taxes on the property had gone unpaid, landing that house and more than 1,000 other properties in the county's annual delinquent tax sale.

For the uninitiated, the annual auction is not quite what it seems. The focus of most buyers at the auction is not acquiring land or homes, but extracting interest payments from delinquent taxpayers.

Winning bidders either get their money back plus an interest payment of up to 12 percent, or they will end up with the deed to the property a year later. In most cases, they get the cash.

"You end up with the interest, or the property," said James Peterson, a Charleston shop owner who has been attending the auctions since 1975. "Either way, you can't lose."

The potential for a 12 percent investment return, at a time when one-year bank certificates of deposit are yielding around 1 percent, holds obvious financial appeal. For the delinquent taxpayer, the interest charges can exceed the cost of two years of property tax bills.

In the wake of the financial crisis and recession, the number of delinquent tax sales soared, from less than 500 in 2006 to more than 1,400 in 2009.

This year, in Charleston County, 1,066 properties went to the delinquent tax sale auction, which began Monday and continues today at the Lonnie Hamilton Public Service Building off Leeds Avenue in North Charleston.

Mobile homes, which are not included in the 1,066 figure, will be sold in a separate auction.

The properties for sale include homes and undeveloped land, private homes and investment properties. Some are owned by nonprofit groups and associations. A few odd properties are little more than rights-of-way that can't be built upon.

"Sometimes, people just don't have the money to pay the tax," said delinquent tax collector Mary Scarborough. "Sometimes, it slipped through the cracks."

And sometimes a property is going through foreclosure, and neither the owner who is being foreclosed upon, nor the lender attempting to claim the property, want to pay the tax bill while the ownership is in question.

If property taxes go unpaid, counties list the associated properties for the delinquent tax sale auction the following year.

Each property goes to the highest bidder, with cash, a money order or a certified check due the same day. Properties that attract no buyers go to the Forfeited Land Commission.

Tax-delinquent owners, and those with liens against their properties, have a year and a day after the sale to "redeem" the property. That means they get to keep it if they pay the overdue taxes, the current year's taxes, associated fees, and an interest payment to the buyer.

Bidders are paid interest of between 3 percent and 12 percent of the auction price, depending on how long an owner waits to redeem a property. Interest is paid on the bid amount, not the tax debt, and is capped at the amount equal of the overdue taxes, plus current year taxes and fees.

If properties are not redeemed then the bidder gets the property, the county gets the tax money and fees, and the prior holder of the deed gets the difference between the taxes owed and the auction price.