Tips and advice..

I'm looking and always interested to have E39. In Malaysia we always have recondition unit from anywhere right hand drive world and sell it with resoanable price. So in summary the car I might purchase will be second or third or fourth hand and you can imagine the condition. Apperance might be very promising but the other side nobody can tell. I would like and appreciate of anybody can give me a tips, advice, what to check, question to ask or anything specific to look for if I want to purchase this model.