if its a private buy, ask whether its been remapped or not, see if its got any uprated parts etc, plus the usuall youd apply to any 2nd hand car.
 
from what i found when i was looking for a cupra

coil pack issues (not sure if its just MY03s)
wet carpets as mentionned
duff OEM stereo's that had a fault
any other receipts of warranty work

general issues when looking at a 2nd hand car in general as mentionned

Heated seats-i dont think any have ever had it
Washer jets for lights-quite safely say no (drives me a bit mad having to clean the lights frequently as i do alot of motorway and long distance trips).

Nice cars, VAG build and reliability so you cant go too far wrong.
 
when i was looking the two main probs seemed to be leaky door seals and coil packs. mines a jan01 and ive had no problems. coil packs were changed by the previous owner under warrenty.
ive been told that early years had poorer dvs. ive put a forge 007p on mine but my stock one seemed ok.

happy hunting! good car choice btw.
 
hey

Coilpack
foggy windows
foggy frontlights
MAF
windowsraisers(expensive to repair at stealers! £375 with labour pr window in Norway )