Oil leaks and more oil leaks... Valve cover gasket, alternator housing gasket... pretty much every gasket in the car. Know what your getting into when buying an older 6 series... and keep a fat emergency expense account! The older ones are inexpensive for a reason.
I used to drive a 2002 745I. Invoice price was $121,000, in 2011 they sell for $10,000! The year I sold it, I spent over $7000 in maintenance! This N62 engine is a beauty, but comes with its issues. Not trying to scare you, but people forget that the cost of the BMW is the maintenance costs, along with the sales price.
Thats why I laid down the lumber and bought mine from the dealer with CPO and only 40,000km.
2012 BMW M6 CONVERTIBLE