The next gold rush in the mortgage industry may be home loans that fall outside the legal safe harbor for qualified mortgages under new rules that took effect in January. And like any bonanza, it’s hard to tell how big the mother lode is. According to Deutsche Bank Securities, it could be a staggering $600 billion a year, but that estimate comes with a lot of caveats. For starters, Deutsche Bank estimated that about $52 billion of 2013 mortgage originations were ...