Lots of stuff nailed to it. Just ask by whom, and how good a job did they do? Ask yourself why? And what's it been used for? I'll bet a pound to a pinch of puppydog poo that it's had a hard life off road. He'll also be looking for the lions share of the 5K he's spent, AS WELL as the value of the original vehicle.
Rear crossmember'll cost you £400 - £600 to get done professionally, and on a 1987 vehicle, there might well be other bits of the chassis which will need attention. (Waxoyl can hide a multitude of sins)
Passenger door doesn't close... Possibly as the A pillar has decomposed internally, or, more likely the steel door frames have beaten it to it. (If it was a simple relocation of the striker or replacement of the catch, then he must be a madman to sell it without sorting it out) £250 for a door - ish, plus paint. The passenger wing's got a crease in it , as has the door. The alingment's almost definitely awry.
As for the leak, they all do that Sir, but make sure the water hasn't sat in a carpet and dissolved the footwells or the floorplates.
Check for regular oil changes, as the V8s do VERY badly on old oil (Cam lobes are made of cinder toffee, and that engine was rebuilt at 95K miles for a reason)
Buy the BEST unmolested one you can, then molest it to your taste, rather than someone elses.
PS It'll get stolen in about 10 minutes anyway, looking like that.
PPS That much ICE with a V8? It's all the soundtrack you'll ever want.