Mini Cooper can be more expensive then a 911 if neglected.
Main isues I've heard about the 02 are Elextric Power Steering Failure, Power Steering cooling fan (may cause fire)
Mushrooming Strut Towers
Midlands Transmission Failure through middle of 2004 (5 speed non-s)
Motor Mount leaks
Rust under door sills
Windsheilds Cracking
Oil Leaks-cheap part, lots of labor
Valve Cover and oil pan leaks
MINI COOPER :: North American Motoring - Oil Leak @ 50k
Here is a link from the NA Mini Cooper forum about higher mileage issues and other stuff
MINI COOPER :: North American Motoring - Should we start a SubForum for High Mileage?
Other then that they are fun cars but IMHO I would have a back-up vehicle unless it was 07 or newer under warranty.