Well, I'm not an expert Jim, but we've had a few recently. (now dried up though, sorry).

Things that potential owners seem concerned about (all of ours have been okay thankfully ) :
Rotten Inner wings
Rotten Strut tops
Cracked Dashboard
Rotten Battery Trays
Rust around windows hidden beneath rubbers

A bit that gets overlooked a lot is the area above the door hinges, seen some with belting great holes there, but I guess that's sortable.

Mechanically, we've had no problems with any of the ones we've had, despite the ages of some, they've been in surprising condition. Seems the majority of the crap ones have gone to the great scrapyard in the sky...