I owned a 2000 323i 4Dr, purchased at 89k miles.
Now all designs have their weaknesses - my model's weakness was the cooling system. When I purchased it, the leather seats in front were partially shot, and the wheels were a mess.I also replaced all 4 window regulators and put 160k over 8 years on the car. Traded it in at 240k when it needed a new windshield, suspension, brakes, and other work.
I budgeted $1800/yr for maintenance on that car - some years, it was less - $800, some it was more - $2500 (with tires). I took it in to a non-BMW shop that worked on Euro cars.
For the first 3.5 years, $250/mo car payment and $150 maintenance budget was a bit much - wouldn't do that again for the condition of that car when purchased.
All I can tell you is that you will spend money every year - I thought $150 per month to drive the car was less than a car payment - so that rationale worked after the note was paid.
Good luck.