There are some things to watch out for on A2s. Here's some that come to mind:
Early A2s had cast iron wishbones with captive ball joints. Later ones had hollow pressed steel ones with replaceable ball joints. However, the pressed steel ones rot from inside and some have collapsed even though they passed an MOT weeks before. So inspect carefully and prod hard. Some people like me have replace the pressed steel ones for the earlier cast ones.
FSIs are well like by those who have a good one but ones not cared for can prove difficult to sort out problems and can empty the wallet. FSH and being run on premium fuel is a must for FSIs. Sometimes sellers will blank out the engine management warning light as this is now an MOT failure. Check the light comes on when the ignition is turned on and then goes out when the engine starts.
Rear axles are beginning to fail with rust if they been subject (for example) to lots of winter salt. Check especially high mileage or vehicles from a coastal area.
Open Sky is much sought after and commands a premium but if not regularly used and lubricated can fail and parts be broken. We have a specialist repairer in the club.
Head linings are beginning to fail after 20 years, especially if the vehicle has been sat in very high temperatures which impacts the glue (common Audi/VW problem I believe). I've just replaced mine. I took it out and removed the old headline and glue (messy job) and then had the "biscuit" professionally covered once I found someone prepared to do it. DIY is hard as impact adhesive is used.
The aluminium exhaust heat sheet is fixed with steel bolts so there is Galvanic corrosion that eats away the aluminium. I replaced mine with alloy bolts and large felt roofing washers with a rubber inset. Note steel bolts on the A2 should be the coated type.
A2 specific parts are getting difficult to get since Audi removed all stock to Germany to Audi Tradition. They no longer export to the UK since Brexit. However, kind member
@Rickmeister who lives in Germany from time to time places an order and he then ships to a member in the UK (or brings it himself) and the UK member then distributes. We also have a number of ethical breakers who only break if they cannot restore. This is useful if new parts are no longer available.
This forum is a very friendly community and has some real experts. See the many "How to" articles.
To search the forum don't use the forum search but use google/duckduckgo etc with a prefix of site:a2oc.net then the <search words>
e.g. site:a2oc.net "how to"
Good luck.