I had completely overlooked the fact that the DE did not know that Voldemort was half-blood. So that may put a spear through my Malfoy owning the house theory. I wonder if Voldemort knows who owns the house, if he was aware that the owner of the house never came there(he was aware that Frank had no wife) and if he hangs out there a lot? Is this where he spends his time in passing?