Really what Taffy said.
No real weaknesses except fuel pump and weak terminals on the oem battery, so if it works it works. 70 degrees are sensitive to geometry and small tweaks and proper springs can transform the bike, so if it's not set up for your weight it can be improved.
So go for the usual stuff; check for leaks, bent stuff, misalignment, loose suspension/wheels, repairs, general impression and don't believe the maintenance schedule the seller claims (check oil level, air filter and how dirty it is and where, it can give you an impression). Read the manual before so you know the bike a bit and check the things mentioned in the maintenance part. Blue bling and new plastics doesn't bring the price up. Worn chain, sprockets, brake pads and wheels can be used for haggling the price but they are parts that are changed out frequently. Don't be afraid of hours, the engines generally cope just fine over time due to big crank bearings and sturdy design in the engine blocks.