Welcome James, Good luck with purchase of your car, best if you can buy the car with full service history, check the condition of the car, if it looks tatty it probably hasn't been well cared for, mileage 10 -12,000 per annum, check fluids and oil, also if the car looks like it has done more mileage than the clock says, Beemers are quite reliable if looked after, you want to test drive the car when the engine is cold and take it for a long drive, everything else is just common sense.