Of the 4 I've bought, the only one I got a test ride on was a KZ650 - I knew the owner & the bike well (he was my boss at the time), which was the only reason I got the test ride. He'd turned it into a cruiser with a full Vetter fairing, a king/queen seat with bags & a trunk, etc. Seems the bike just got slower & slower as he & his wife put on a combined weight that matched the bike's.
He threw in all the goodies required to turn it into a KZ650C, knew that it would be a good bike for my then 160lb frame, & he wanted me to buy it, so ...
What's typical around here is a buy-back offer, but I've never allowed anybody to ride away on a bike that I hadn't signed over & pocketed the cash for, & I've never expected that as a buyer. Signing the title makes a buy-back a little sketchy, but I'd rather do that than deal with the decedent's lawyers.