Sorry, totally missed the mileage the first go-round. OK, assuming they haven't done anything to maintain the car, you'll need to:
1) replace all the old fluids and filters
2) replace the spark plugs
3) you'll probably see the camshaft sensors fail in the near future
4) oxygen sensors are getting old (recommended replacement is at 100K)
5) check the brake rotors for thickness. if they have a noticeable lip around the outside edge, they'll need to be replaced soon
6) the final stage unit might start acting up
7) the water pump may be nearing the end of it's life (if it's the old plastic propeller style)
8) if you have a volt-meter, you can check the current off the battery to see if it needs replacing soon
9) if you feel any front-end shakes or shimmies, it could be due to torn ball joints in the control arms, or misaligned wheels.
10) check the undercarriage, bottom of front bumper and bottom of mudflaps for scrapes, a sure sign the car was driven hard and bottomed-out.
Pay a local mechanic who works on foreign cars to look it over well. Take any issues to the owner and negotiate as needed from there. If you have access to some mechanics tools and a Bentley manual then there's really nothing in the above list you can't fix yourself and save some cash. If you're not mechanically inclined, then Bimmers (like old people) can be expensive to maintain in their later years.