You will need to lower it if you get new alloys - i've got 18" RS4s on mine but not lowered it yet! It desperately needs it! I'm going to opt for eibach springs i think, seem to offer a decent drop (between 30-40mm) without causing any problems.
To be honest it hasn't cost me much, the main thing to look out for like i say is the timing belt - this had not been done on mine but i got some cash off the price because of it (it'll cost you around £300). If it's not been done it will probably need it on a car that age so use it as a bargaining tool.
Other than that, all i've replaced so far is Engine coolant temp sensor (£20 for the part - easy to fit) but the passenger Door lock mechanism does need replacing (about £70 for new mech i think - more difficult to repair yourself but do-able with a spare afternoon) and just this week found out it needs new Cam Shaft Position Sensor and new Lambda Probe. (both about £70-£80ish for the part i think).
I wouldn't let this put you off, the various engine sensors seem to be the most common faults (the MAF being the most common) but they're all easily replaced and don't cost that much and some of them may even already have been replaced on the car you end up buying.
