Try and get one with some history.
Check for rust round the scuttle panel at the bottom of the windscreen, and around the rear number plate lights.
Check the inner wings and for creases & under the fuse box and expansion tank.
Engines are generally strong but need to have been looked after, same for transmission and diff.
These cars are getting on a bit now so no doubt it will require some maintanence, there not the cheapest of car to run, but they are one of the best drivers cars there is.
If you have got any particular question you want answered I will do my best to help
<img src='http://www.bmwmregistry.com/userimages/6dd4ba9350aa7dbe4668e60ed4afdbd2/Sig%2BPic%2B2.1.jpg' border='0' alt='user posted image'>