Rust is the big enemy. Start at the top and give the roof (especially those with opening sections) a good going over, before checking the cab and chassis.
Provided that the engine has been well maintained it should give you years of use. Lift the engine lid and if there is a black film of oil covering everything then start asking questions. An oft-overlooked aspect is the rubber seal around the engine tinware as you don’t want it to get too hot in there.
Many would-be camper owners buy with their hearts rather than their heads – don’t! Vehicles that look ‘cute’ with reasonable looking bodies and good condition interiors can turn out to be death-traps with useless brakes and rotting chassis. Find someone who knows what they are looking for with an air-cooled vehicle and heed their advice. Everything can be done to a T2 but the costs soon mount up!