Once a site or blog is created and optimized for SEO (search engine optimization) purposes, the search engine marketing (SEM) begins.
The potential for earning income in this area is literally through the roof if you know what you're doing. An expert in SEO management is responsible for successfully marketing a website and can choose to promote it in a variety of ways.
Some of these promotion techniques may include article marketing, social bookmarking, forum posting, writing press releases, submitting your site to a number of search engines and directories, and blog posting; just to name a few. Most businesses don't pay their own staff to perform these tasks and choose to outsource all their SEO and SEM tasks instead.