18-21 is that sensitive age where boys think they're men, but they're not there yet. A firm hand from either the mother or the father is necessary, because they still need to be controlled.
Walk in when he's playing, and switch the power off. Tell him you won't allow him to play until he contributes to the house. He is to find a job, and until he does, he will clean the house, mow the lawn, or wash up. Whatever you need.