Most e46's have the same 8-10 common issues and straight forward fixes. Each series like 320-325-330 and so on offer differing advantages like power,suspension and so on. Nothing incredibly important to avoid really besides DO NOT drive the car once over heating!
As stated they all have gremlins, expect that but if properly serviced (do not follow bmw service indicators of 25000) youll be fine.
Good luck and here's to hoping buying a car unseen/scanned or looked over first doesnt cost you. You could quite easily save $XXXX and just as easily spend $XXXX in needed repair. Frankly I would not go this route but it is your money.