Ready or not, here come those zero down loans again. I blogged here a few weeks ago about a new mortgage program MassHousing rolled out over the summer, with the backing of Fannie Mae, under which borrowers don’t have to fork over a down payment. I noted the initiative comes with the federally-controlled housing finance behemoth already in hot water amid a sharp spike in defaults. Upon some further reporting on my part, it turns out these new, no-money-down mortgages are taking off fast here in the Bay State. (As far as cash up front, the only requirement is ponying up $1,000 in advance toward closing costs.)