I would like to earn a little extra money from my website by selling links on site. Would Google know these links are paid links? Is there some type of penalty?
Buying or selling links that pass PageRank can dilute the quality of search results. If you believe a site is engaged in buying or selling links that pass PageRank, please tell us about it. Buying or selling links that pass PageRank is in violation of Google's Webmaster Guidelines and can negatively impact a site's ranking in search results.