No, it happens when the forum gets incredibly large and the Admin cant be there to Mod the forum his or herself so, they get some outside help.
As for "stock". "Fancy" forums have sponsors that help pay for webspace and special features. The sponsor is allowed to advertise on the forum by a banner, ad or whatever and in turn they help with the finances to keep the community up and running. You could use free forum space like ezboard.com, but most people put up and maintain the forum themselves.
I belong to another forum that has well over 10,00 members (real big forum!!) It has over 10 mods or so. Above the main forum page are ads and banners. Thats what the ads and banners are for. It can be used to help keep the forum free for all users. Hope that helps.