Need advice on a potential deal

[Minna Reid]

Guy calls me yesterday, going through a divorce they want to liquidate fast. From my number crunching we're in my ballpark at a 1900 sq ft house, I'm going to check it out in a few hours. Now heres the problem. The town list this house as 1000 sq ft. He says he finished the attic, added beds and a bath, house is now 1900 sq ft. However town hall says he never pulled permits for any of this as last permit he had was to add a dormer and roof only.
So sounds to me like we got an illegal fin attic. I'm not sure how this would affect me exactly, except that if I need to resell the place as a 1000 sq ft house, I got big problems. What do I do?