So normal things like full main dealer service history is very desirable.....check the history as it should be serviced every year but often people do it at two year intervals due to the low mileage they've done.
So things to look out for are shocks wear out prematurely due to the 'mag ride' so check for leaks/misting on shocks (you can send them to Poland for reconditioning)....before 2012 they can develop a crack in the chassis, after 2012 they put strengthening plates in, also if the air conditioning compressor fails it's can be an engine out job due to it's location and depending on V8 or V10 is a 10-40 hour job so check the air conditioning is working.
If you google any of the above key words you will get more details.
Also if your interested in it get it booked into Audi for a FREE....Yes FREE health check they give it a once over to see if it needs any work doing. Go to audi.co.uk and do a search on health checks.....
Surprisingly for a 'super car' they are on the cheaper side to maintain as they share some components with other Audi's....don't get me wrong compared to running a Ford Focus it's expensive bu not a Ferrari or Lambo !!