Stator and regulator charging failure
Stators and regulators on the V4 fail with depressing regularity — ApriliaForum charging-failure threads run to hundreds of owners, and Aprilia revised the parts more than once. Check for 13.8-14.5 volts at the battery around 4,000 rpm and ask for receipts showing an updated stator or aftermarket MOSFET regulator. A dying charging system strands the bike with little warning.
Ask for repair records covering this item. If it hasn't been addressed and the car is in or near the mileage window, price the $550–$1,100 repair into your offer — or make it the seller's problem.