1, Never shop on Fakebook.
2. Never bring cash to strangers in an alley.
3. Don’t shop on Fakebook.
I too always meet customers at either The Courthouse or The Sheriff’s Offices/County Jail. AND I am always armed - visibly and concealed.
I have done hundreds of transactions on FB Marketplace, without incident, or even fear of an incident.
It’s not hard to do a little DD on your buyer/seller, to establish credibility.
That said, I don’t buy/sell cellphones, subwoofers, gold spinner wheels, etc.
(I always carry)