Two things that jump out to me are frame rust and the state of the cooling system. To me, significant rust on the frame would be a deal-breaker.
At that mileage, I would expect to see new cooling system components. A new radiator / hoses / water pump / etc., are all things to expect to be replacing (if it hasn't already happened). My 2013 developed a leak in the "valley" under the intake manifold at about 95K miles. It started to leak coolant without actually dripping anything on the ground.
I would say that if this truck has not had cooling components replaced, you should expect to be replacing them. Not a big deal, but something to consider.
Lastly, I would say that you should ask to see records that document replacement of drivetrain fluids. At that mileage, I would expect the transmission / differential fluids to have been changed at least once.