If it's not too big of a deal, I'd take it to an Indie BMW Mechanic or BMW Dealer and have a pre-purchase inspection done on it. Find out things like if the radiator's expansion tank has a hairline crack and gushes out fluid when it gets up to temp.........
Also if any of the windows roll up slowly (and makes some god awful noise), usually means the regulator is on the way out (I believe this is a common problem on e46's).