What about a private seller that happens to have a lot of shop experience? I am the only person to have touched any of my bikes with a tool in over a decade. OTOH, claiming to be a bike mechanic in an ad doesn't always weigh a lot to me, I've met all manner of bike shop mechanics and 'mechanics' (and they are free to have their opinions of me). All that matters when I am looking at bicycles is what I (or a trusted and more knowledgeable person standing literally right next to me) can see.

I understand the buyer being conscientious by getting a second opinion, but haggling down a price and THEN needing to set up a big meeting of indeterminate length during the business day to decide if he's going to buy the item is poor form in my book. If he (or he and a friend or whatever) can't come look at the item and establish its value on their own, why do they deserve to haggle?