Aloha. I just bought a used 325i 2006 from a old lady with 51854 miles on it. The interior is very nice seats look brand new, the exterior needs work car was washed at a junk car wash and the paint never been polished. Spent 4300 at the dealer for belt tensioner and belts, valve cover gasket, new injector, new expansion tank and hoses, Not counting new struts and shocks when they come in. This is my project car. I owned a 96 Z3 which I gave to my daughter which I blinged out, when she turned 16 What better way to learn how to drive a manual transmission then in a Z3 the clutch and gearbox is so smooth.
Your vehicle uses condition based service. So you will need to access the service information through your instrument cluster to see what services are due. I also recommend a coolant flush every 3 years, rear diff fluid service and transmission service, power steering flush.