Crack Resell

Listen up, smarty pants. This joke is saying that a prostitute can clean and resell crack. You see, "crack" has two meanings here. It can mean crack cocaine, but it also refers to the prostitute's, uh, you know... rear end. You probably do NOT have one of those, so, uh, good for you, loser. By "wash their crack and resell it," the joke is saying that the prostitute can clean herself up and then have sex with another person for money. Do you get it now? I bet you don't.