Characters purchased may be resold for their original purchase price. You may add onto the price if you've drawn or purchased art for them, to recoup some of those costs. They may also be traded or gifted.
Characters acquired in a trade may only be traded or gifted. You may trade for designs, art, or physical goods.
Characters acquired as a gift may only be regifted unless you've drawn or purchased art for them, in which case you may trade them away.