Definitely try to locate the vehicle's maintenance history and I agree with several items mentioned already, especially window regulators, driver's door carrier, and expansion tank. I would also inquire about the front driveshaft and transfer case because of the short spline condition of the early driveshafts. Keep a close eye on those front CV boots and have them replaced at first signs of cracking. As long as there is grease in the boot, you don't have to worry about replacing the axle. Tensioner and idler pulleys on the serpentine belt seem to go around the mileage you're at too.

2002 X5 3.0 236,000 miles
2004 325i 105,000 miles