The vanos system is going to be an issue on any BMW equipped with it, just make sure its been serviced at the proper intervals (I believe it needs to be adjusted every 60k miles). When you go to test drive it make sure its a cold a start and listen for any rattling or ticking coming from the head. Now I'm no BMW mechanic; I used to work in the service department at a BMW dealership and I'm just telling you what I know off the top of my head. A properly maintained BMW will last FOREVER, an unmaintained one, well lets just say I've seen engine replacements at 30k miles.