There isn't anything to worry about with the bodywork when buying this generation of RS6. Aside from the usual checks for tight, even panel gaps and any signs of crash repairs, it should be flawless. Some stone chipping on the aluminium bonnet is not unusual, but otherwise it's a hard-wearing machine.
With the Avant estate, check the rear load sill for any signs of scratches from heavy bags or dogs getting in and out.
The only other item to check are the headlights, which can suffer from misalignment, so be sure they illuminate the road ahead properly.
PHer's view:
"The Avant is the one to have in my book. Who would ever suspect an estate car of being this fast?"
Terry Amory