Affiliate marketing can be a profitable business venture, but it can also be a difficult way to make money. The vast majority of people who attempt to earn money through affiliate marketing do so using a variety of tools – pay per click advertising, custom Websites, and e-mail marketing campaigns. Most of the well known successful marketers rely heavily on e-mail marketing as it is easier to generate sales from existing customers than it is to find new ones. The downside to this technique is that building a sizable mailing list can take years.