In this video you will learn what a Google sees as a paid link. In a simple sense, you do not want to get involved with getting paid links! They will hurt your ranking efforts big time if Google catches you because you will be penalized. They do not like paid links because they are attempts at manipulating their search engine results. So watch this and learn about them. Here is the link I reference in this video with Matt Cutts talking about spam.
This is part of the Ultimate Real Estate Link Building Guide
