Okay so I was visiting an internet marketing forum and one of the members asked if mini sites still worked. I've found that the consensus answer is that yes, mini sites do work. There's tons of marketers who swear by mini sites.
The good thing about mini sites is that you don't need pages upon pages to rank well in the search engines. You can actually grab the number position for your keyword with just one page.
Creating multiple mini sites and monetizing them with Adsense is the way to go.