I started a ROM site when I was 14, it eventually got really popular and thus got quite a few youtube videos and good search engine rankings. These days the ROMs have been long removed so traffic has obviously fallen, however due to the links and still decent search engine rankings it gets roughly 100k page views per day. End result is that the ads give me around $2k to $3k a month. Pretty happy with that since I no longer work on it and it's basically just rotting away.