Sounds like you are selling virtual credit cards. Once you received the escrows payment you can't send a physical card at all. And what about the risk of you discharging the card?
I would not know how to be safe of that offer.
You set the PIN on the card. Its perfectly possible for me to send the card after receiving escrow payment.
Yes, it might be that there is a physical card, but it could be the case too that no physical card exists or can exist.
You set the pin on the card? So the new owner has a banking login then?
I only say it sounds a bit like it could be a VCC only. And an escrow could not do anything against it anymore when the physical card has to reach after release of held coins.
He buys Vanilla Visas etc at 350 and wants to sell them at a facevalue of 500 most of this cards come from fraud so beware