Rust. Rust. Rust. Corners of the engine bay where the inner fenders meet cowl, check the cowl, inner and outer rockers, rear quarter panel seams, kick panels, bottom of tailgate, and bottom of taillight panels. Almost all have floor pan rust so that shouldn't be a big deal for you. You said he replaced the metal but check and see if the work was done well.
Aside from that, the rest is standard fare. If he says X, Y, Z was rebuilt assume it wasn't unless he has receipts for it. Everything can be rebuilt but for your first one hold out for a good one. Pictures of anything that he calls "restored". As Bajafresh says "if you can't afford a good one you sure can't afford a bad one". Good luck and post pics.
