Oh and, make sure you click Cash on Delivery, cuz if you don't, you end up sending the money .__. Most of the time, they wont refund the money nor the items.
If a person asks to borrow a weapon or a costume, DON'T DO IT. You wont get it back. If they continue to annoy you about letting them try it and start spamming, screenshot it and report them. In terms of business, don't be nice and tell them to pay you later. Either have it now or no deal, don't trust people unless they already have a good reputation.