Stator and regulator/rectifier charging failure
The charging system is marginal: stators and regulator/rectifiers burn out and strand riders with a dead battery, per NHTSA complaints and heavy forum consensus. Put a voltmeter on the battery — you want around 14 volts with the engine at 3,000 rpm. Receipts for a new stator or an upgraded regulator/rectifier are a plus; dimming lights or a weak battery are warning signs.
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 $400–$800 repair into your offer — or make it the seller's problem.