For a sector that originates, at best, $5 billion a year, the fledgling subprime mortgage industry is garnering a bit of attention these days, though most investors do not publicize their interest. One nonprime executive who has received funding and spoke under the condition his name not be used described his suitors as hedge funds, private-equity firms and real estate investment trusts. He also mentioned “rich” individuals looking to put money to work. To date, the largest investment in a subprime/non-agency lender appears...