(RECAP: The number of big real estate companies involved in renting single-family residences is growing. New York-based financial services Blackstone Group L.P. is now the largest landlord of single-family homes, having spent roughly $8 billion over the last two years buying 43,000 homes. California-based American Homes 4 Rent, the second largest such firm, started in 2012 and now owns more than 25,000 homes in 22 states. Plummeting home prices in recent years opened the door to the investment opportunity, said Dave Bragg, managing director of the residential research team at Green Street Advisors. Meanwhile, the armies of homeowners who saw their residences foreclosed still needed housing.)