I've never sold a plane. I usually have loaned them to friend and they've wrecked them. However, one thing a broker does well is vet potential buyers. You don't want to have some mechanic you've never seen tear your plane down for a prebuy, the buyer walks away (or ghosts you) and the mechanic has a lien on your plane. One broker I spoke with has a contract the machanic must sign releasing any right to put a lean on the plane before they start. He encourages them to get money up front from the bujyer.
Unfortunately I think there are people out there that are much more talk than action; and I bet a lot of them are perpetual airplane "buyers". Of course you also get the guy who thinks that a 40 year old plane for $100,000 should be in the same shape as his brand new BMW for the same price.