Hi Bradley, your not thinking of getting rid of the a4 now are you?!
Obviously check service history, this ideally should be full and check to see if the cambelt and water pump has been changed as on the age of cars you'll be looking at, they should all be due or have had them changed.
Also make sure all electronic items work as they can be expensive to fix.
Are you thinking of manual or auto? And are you wanting Quattro?
Cheers
Steve