How difficult is it now to get a mortgage with no money down?
When I bought a two-family house about four years ago, the mortgage company allowed us to count 75% of the documented historical rent on the rental unit towards our income when calculating our loan qualifications. As 45moore says above, this probably only applies if you are buying a multi-unit dwelling. In any case, a quick call to a mortgage broker should clear this all up. It may be that your boyfriend missed his opportunity to get a house without a down payment. Given that housing prices are on a downward trend with no bottom in sight, it’s hard to see why a lender would want to issue a mortgage that would almost immediately be underwater (i.e. more than you or they could recover by selling the house, especially when considering sales costs). But still, it may be possible, and a mortgage broker would be able to give you the definitive answer.