The private-equity firm Blackstone Group LP has spent $7.5 billion snapping up 40,000 distressed homes over the last two years to assemble the largest single-family rental business in the U.S. With the help of Deutsche Bank, JPMorgan Chase and Credit Suisse, it could begin moving forward any day now with the sale of almost $500 million in bonds backed by lease payments from those properties, the first such real estate owned to rental securitization transaction ever put together. The firms have been fairly tight-lipped about the deal, which has been in the works for months, but tidbits have been leaking out in dribs and drabs. According to media reports, the deal will be backed...