When Frank Sledge took out a mortgage on the eve of the 2008-09 recession, he set off a series of personal disasters that ended in bankruptcy, foreclosure and ejection from his Florida home. Unable to obtain another loan, Sledge thought the door to home ownership had slammed shut. But then a company backed by Wall Street investors made him an enticing offer: it would buy a house of his choice and rent it to him, with the promise that he could purchase the property for a fixed price if he came up with the money within five years. “I thought the value of the house would go up,” says Sledge,…