When you have something for sale and a person is asking questions about it's condition before buying, and someone P.M.'s them saying "I'll take it" why not tell them that you are discussing it with someone, and I can tell you withing the next 5 mins if is still available. Instead of selling it out from under them?
If they are a serious buyer, they still will be in a few minutes.
Better yet why not prepare your ad and give a complete description and photos in the first place?
I would wait a little longer, but many of the modern sociali transactions are too fast. Patience is lacking in general nowadays. Take notes and don't interact with that seller again or put them on your Hide Me list.
