Don't pay until the item is ready to ship. Simple as that.
As Tony mentioned, sometimes prop builders get in a jam. When you report the situation to paypal or credit card companies, you may just end up making the situation worse.
I had a member, some years back, file a dispute for a prop that was lost in the mail. I went to give him a refund, but my account was froze. The prop came back to me because the member had given me the wrong postal code. It was a large box, and I couldn't send it back because my only credit card (paypal card) was frozen. After two hours on the phone with paypal, I was able to get a refund out to the guy, but I needed to send photographic evidence that the package was returned. It took two weeks after to get my card active again.
The member got back to me, wanting the mask, but I wouldn't sell until he contacted paypal to clean up his dispute. He never did.