just a sidenote, you're not selling a product. You're offering a service and only asking a small payment for your time, no items //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif you give them the design free after they pay for your time spent doing it.
so there, technically you still do NOT need to be a vendor. keep up the good work man!