Here you have a piece of art you are selling and make a face to face meeting and secure a deal. Let’s say you agree on 30 $ETH for the painting. (All sales will be in crypto, ususally $ETH, $SOL, or $Matic.)
Then you go to ArtStandardMedia.com, you enter all the terms of the deal into a smart contract at the agreed price. That session creates a single NFT for this transaction, with specific terms and price according to the negotiation.
So you are HOLDING the NFT and the artwork while you wait for NFT transaction to complete.
Once the NFT is Purchased via Crypto transaction, you can release the painting. You can even put royalties % in there so future sales would net you some income.
Then the new buyer has the NFT and the Painting!
