Update - Bought a Demon project - WWYD?

Based on the condition of the floors, I doubt the frame rails are in very good shape. It looks like the rust is creeping all the way up behind the kick panel, which would make me believe there is some serious corrosion in and around the subframes in the front, as well as the rocker panels.

It really depends how good you are with body work. I paid $560 for my car and it was in better shape cosmetically- no drivetrain though. It was just a roller. Even as good as it looked, it cost me almost $4k in getting the exterior body work done- that doesn't include the floors and engine bay work I did myself. I would definitely consider the costs associated with replacing the rusty panels. They add up quickly.

Good luck either way. Maybe it looks better underneath then it does inside.