WoW Guides are one of the most powerful markets in the web for making money.
This guy was selling a really nice guide to make money from MMORPG's on ebay a couple years ago that was really good. I actually made about $1,500 a month selling in game items from Guild Wars back when eBay still allowed virtual items. I flipped one WoW account that I bought off eBay, but there isn't the money in it that there was a couple years ago. I did set up a site for the Warhammer guides, but I haven't dedicated much time to it, so I'm not sure how much interest there is out there. If you are really interested in gaming the best thing to do would be write your own guide and let other people sell it for you.Thre is tons of mony to make on MMORPG's
A blog to check out is this one: http://looterslounge.blogspot.com/
He has great ideas, and alot of stuff on RMT ( Real mony transfers (Selling mmorpg stuff for mony)).
I'm not sure WoW is the game to go for. I predict Warhammer online will out grow World of Warcraft within the next few years. Get in now - from the start and make some mony on it.