You may want to check to make sure you don't run into permiting problems for cunducting a commercial activity in public lands. Some agencies may have strict prohibitions, while others may have permit systems to control what gets sold on their properties. We, for example, have a vendor permiting system in which you would need to obtain a permit prior to this type of selling. It doesn't cost much and the restrictions are minor, but it gives us a chance to filter/limit commerical activity.