I work on several freelancing sites and I keep noticing job in SEO/Link building area. I am interesting in learning how to do this kind of projects, because I noticed that the fees involved are pretty big (take a look bit.ly/h5Ke1S for example). I understood that in most cases, they want someone to create backlinks that should match certain criterias, like being dofollow for example. How could I get dofollow links on some keywords without owning lots of sites?