10 posts, IIRC, for links in posts. At the moment, you can add a link to your signature immediately and for members who are obviously here to be a part of the forum itself, we're happy for them to link away in their signatures without a further word from us. From your own perspective, we do have a section on the forum for promoting business and websites (beats me why the backlinkers don't use it if they actually have something to offer!) if you don't have a site to link to on your signature yet.