I have learned through experience that it is ALWAYS best to have the car checked out prior to purchase. Your best bet would be to have the seller take it to the local BMW dealership and have a used car inspection done. Cost approx $150.00 for a visual inspection and around 300 for a full mechanical inspection. There are just soooo many things that can be hiden by a seller in photos. Not that every seller is like this but out of the 5 Beemers I have purchased on-line two were bad. Hence, this is where I have learned the hard way through experience. If the seller is truly honest he/she should have no problem doing this for you. You can talk and pay directly the dealership and have them fax you the report.
Hope this helps and good luck with your puchase.
2004 325ci (SOLD)
1995 540i (FOR SALE)
1989 325 Convertible (Track Car)