Another Outfitter owner here - but mine is a 2011. I think you need to look at all the things you would look at in any 11 year old camper. At that age, the way it was stored, used and maintained is more important than the original build quality.
Open up everything and anything and look inside and behind. Everything should be nice and dry; especially the lower portions. And, of course, everything should work as expected. Have the seller show and demonstrate everything; that way you will see how well they know the camper and how they treat it.
Check for delaminations in the walls. There should be no bubbles inside or out. If there are, clarify what they are and if they will grow bigger. They can be just poor manufcturing; but they can also indicate a leak.
There were a number of changes throughout the years. At some time after 2010, they went from a multipiece TPO roof to a one-piece fiberglass unit. On my 2011, the outside walls are some sort of fiberglass, not wood backed. I am not sure if they were the same material throughout the production years.
Check the Weblon softwall for wear from the inside. Mine tends to get caught in the roof lift mechanism and shows some use in one place.
Personally, I love my Outfitter for its ingenious design and ruggedness. You will be surprised how much storage space there is inside. The build quality and fit & finish were not so great on my sample. But I am stil very happy with it as it does exactly what I expect from a camper.