I have bought and sold a LOT of things on FB Marketplace and Craig's list.
A while back I had a generator for sale on Marketplace and got a call from a guy about noon. After I answered some questions about it he said: "I get off work at 4:30 and I can come then". I said OK, call me when you get off and if I still have it I'll give you my address.
Less than 5 minutes later I get another call from somebody else. He said "I want the generator. I have cash in hand and can be there in about an hour. I am in XXXXX (about 50 miles away). Would you hold it for me till I can get there?" I said if you can assure me you'll be here in less than 1 1/2 hours I will hold it for you. If you're not here by 2:00 it's first come, first served. He said OK, I'm headed your way.
Well, as soon as I got off the phone with the second guy, the first guy calls back and says "I need your address. I got off work early so I could come buy your generator". I apologized to him and told him I promised the other guy I wouldn't sell it till he could drive from XXXXX. Well, he came unglued and begged me to sell it to him first as he was nearby. I said I'm sorry but I gave my word to hold it till 2:00. If he hasn't shown up by then I'll call you back. I said "If you had told me you were taking off work and was on your way I would have made the same promise to you. I am a man of my word".
I really felt bad for the man but I can understand the other guy driving for an hour and find out I sold it out from under him. End of story: The #2 guy got here at 1:35 and bought the generator. I called guy #1 back and said I'm sorry, the generator is sold. By then he was calmed down. He said "That's ok, I'm on my way to buy a new one."
All's well that ends well I guess.