Hi, my husband and I are exploring getting a Dish Satellite for our rv in the winter for 3 months each year. We are thinking of using the prepaid green dot card. Do we need to have a Dish500 to be able to use the prepaid cards or will any Dish Satellite do. Can we purchase a used one? Any help would be greatly appreciated. Have never been on a forum before so not quite sure how to do all this. Thanks again.