The city, which still has a vast housing footprint left over from an era when it had more than twice as many residents, has acquired numerous homes over many years after they fell into foreclosure or otherwise came off the tax rolls. The city’s land bank authority is also now actively pursuing other abandoned homes — about 50 a week, Mr. Duggan said — through nuisance abatement proceedings.

Yet in a city where investors have sometimes swept up properties for as little as $500, only to let them fall further into disrepair, the rules of this auction are strict. Buyers must pay 10 percent of the price within 72 hours; close on the deal in 60 or 90 days, depending on the purchase price; present a contract for repairs a month after closing; and have the home occupied in six months. Many of the homes are in disrepair, but the essential structures are sound.

The city is concentrating its efforts in individual neighborhoods, one by one. “You won’t buy a vacant house on a block if there are three others still there, but what we’re doing is addressing all the vacant houses at once,” Mr. Duggan said. “And people are getting really good buys. These are houses that would be going for $200,000, $250,000 in the suburbs.”