I know a number of friends who are on forums dedicated to 18+ RPs. They warn against any minors joining and even guests can't see into certain subforums without first making an account and reading all of the rules. You're just better off joining one of them. A few of them use forum hosts or RP via Tumblr, so it all depends on you. If you don't want to do that, just stick to the 1x1 section and move the steamy parts to the PM system.