Screw IOUs

So someone on DA was interested in my Star Fox cosplay and, well... here is how the conversation went down:

Them: "How did you make that? I want one."
Me: "If you want one you should learn to sew like me or you could commission someone to make it for you"
Them: "Okay, can you make one for me?"
Me: "It will cost you a pretty penny but if you are serious you can send me a note."
Them: "Well, I don't have any money right now so can I get it now? I will pay you like 200 for it."

Are you serious?! How many people like this am I going to run into? I mean, it was bad enough being called an 'uncivil, mercenary artist' because I didn't agree with another guy's trade, but now someone wants me to make them a free costume and I'll just hope they pay me back when they get the money? Sorry pal, but I don't deal in IOU's, that is just not how commissions work.

End