I have a website, I started it as a fan-site, but it has grown and I was wondering with how many visitors I can start getting money for advertising on my site. I'm not really looking for a profit (but I'll take it if I find it), just something to pay for the costs of running the site. I don't really know anything about advertising, but I'd like ads based on impression instead of click-troughs.

Any help would be appreciated!