Dear benny,
Gearnofear is correct.
The parts for BMW are little more expensive but durable.
Most workshops dont want to repair BMW,coz they may not be specialised in these cars.or the cannot find the original parts in local spare parts shops.
When buying from dealers,they cannot make much profit on the spares.
So some will avoid all this hassle.
In your case,if u compare 5 series and 3 series,it will be little difference in price for maintainace and repairs.
the 2001 -530i with 100k miles which u had mentioned,can serve u another 200k miles provided you maintain it and renew the bushings and carry out minor repairs in time.
BMW cars are reliable,luxurious and durable.
U can try one.Good luck.