Off of the top of my head, it doesn't sound like a good deal to me.
$16K with 18,000+ miles?? At that price, it better have a whole bunch of other goodies hanging on it (crash bars, side bags, etc.) For just a little more, you could buy a brand new one with a full warranty.
AMA - BMW MOA
'07 Honda GL1800A Gold Wing
'14 Ford F-450 PLATINUM
'14 Dutchmen VOLTAGE 3200 5th Wheel Toy Hauler