No comps dilemma. Can you get a mortgage with only 1 comp?

[Frank Jones]

My son is trying to buy his first duplex using a 3.6% down FHA 30 year mortgage. He's going to live in half while he does some remodeling. His offer has been accepted and he has been pre approved for the mortgage. His problem is, the area where this duplex is has very few duplexes and the appraiser can only find one comparable sale. Our mortgage broker doesn't feel like the mortgage will fly without more comps. Any suggestions?