Did he opt for the extended GTPP warranty?
if he did not, and it is out of warranty now, it may be best to pass, unless you can get some extension.
@ 16k, it should have had already 4 factory service updates, the headlight knobs, side bag latch replacements, the rear luggage rack, and the rear brake pedal mechanism recall repairs. Does it have those done?
I would inquire of the dealer where it was purchased (used w/ 12k) about warranty.
the price seems ok IF it had ABS, but you may be at a point where a bike with a warranty, with ABS, is worth $1k more in my opinion.