And in December, just when local officials thought things couldn’t get worse, Cuyahoga County, which includes Cleveland, posted a record number of foreclosure filings. The number of empty houses is so staggeringly high that no one has an accurate count. The city estimates that 10,000 houses, or 1 in 13, are vacant. The county treasurer says it’s more likely 15,000. Most of the vacant houses are owned by lenders who foreclosed on the properties and by the wholesalers who are now sweeping in to pick up houses in bulk, as if they were trading in baseball cards.