I've never seen anyone volunteer to actually make the shirts for another DISer....it may have happened but generally the DISigners just DISign and then it is up to the requester to copy the DISign, print it and iron on any shirts that they have purchased.
Besides, it would get someone in serious trouble with DISNEY if money exchanged hands!! All the DISNEY images are copyrighted after all and the "for personal use" would no longer apply. Not a lawyer but don't think this would be an option!