Try and go for an 04 plate or newer....As IF it has a sub frame/boot floor issue then BMW will 99.9% repair it FOC as a good will gesture as its a VERY publisised issue and they are aware of it. If its under 10 years this will apply. They like to see BMW Service history with it or at least specialists. I know a few people that have had this done.

Its always worth getting it checked prior to buying the car as its a good negotiating point. I had mine checked and all was fine so BMW put it in writing and i had it as proof for the buyer.

Alot of people sell these when they need discs and pads all round and rear tyres......Thats how i got mine at such a good deal.
To replace the discs and pads all round with genuine parts it was £500 (Genuine ATE discs from GSF/ECP are what they fit OE)....so not that dear really...people think they are alot dearer but shop around and you can be the one with the better deal.

Rear tyres for mine were £450...They were Bridgestone RE050's to match the front.....again not really that dear when you look at the car.

Rear exhaust clamps always rot away and fall apart...you can see this through the passenger rear arch....... If BMW wanted to replace these clamps then they will say the only way is a new centre section and rear exhaust at £1200..........Every M3 owner who goes on M3Cutters with this issue have replaced them with Peugeot Clamps at £6.......And they fit alot better. I have done a write up on the cutter site for it.

Vanos issues can be prevented with £15.........buy changing the Vanos filter that takes about 30 seconds and 9/10 times has never been changed and if full of gunk.