I just purchased a 95 525i the other day. It's nice, I'm enjoying it so far. I'd say make sure to take it to a good BMW mechanic first. From what I understand, the cooling system is kinda troublesome in this car so you might want to see if his radiator/thermostat and housing have been replaced, those are known to fail. Plus front control arms and suspension I've heard aren't built as sturdy as the rest of the car, so might want to check that out. And check for signs that the engine has ever overheated, blown head gasket could occur, warped or cracked block and such which are serious problems. And I'd make sure to get a new battery and test drive it to make sure everything seems good. Other than those things, from what everyone's told me these cars are built like a rock. How much is he asking for it?
Wherever you go, there you are