These sites place well in the search engines because they are content-based. Most often, articles are keyword-focused, meaning each article focuses on one word or phrase. Once the sites are indexed by the search engines, and once marketers drive traffic to the site, they leave it alone, let it run itself, and create another Adsense site. It isn't unusual for a marketer to have 50 or more of these sites scattered all over the internet.

The way the marketer makes money from these sites is via the Adsense ads. Because the ads are served based on the content, the ads are targeted. That means that if someone finds your site from the search engine, they are interested in your niche (because they were the ones searching!). Thus, they are also interested in the ads on your site. When they click on one (or more), you are paid a fraction of the advertising cost Google takes in.

For example, suppose you set up a site focused on baseball. You choose to target the "American League East Division" as your focus. You could put up one article on each team-Boston Red Sox, New York Yankees, Baltimore Orioles, Toronto Blue Jays, and Tampa Bay Devil Rays-and an RSS feed that collects news on each team. Put this feed on each page, so each page is constantly updated (to bring readers back). Then, add your Adsense code. Likely, the ads will be about baseball apparel or tickets, things people interested in this topic would be interested in.

As people interested in baseball, and especially AL East teams, find your site, they will read and possibly bookmark the site or add it to their RSS reader. Even better, they will probably click on your ads and you will make money.

You can set up a site like this in one day - get a web host, an Adsense account, and put up five articles. That's it. If you don't have articles or don't want to write them, you can inexpensively pay someone to write them for you.

Put it together, then move on to the next site.