Before I talk about some of the methods for making money online, I wanted to address the role of pain versus pleasure. Every decision that we make in life is weighed on a pain-versus-pleasure scale. We will always do more to avoid pain than we will to gain pleasure, plain and simple. However, this is also what holds us back from succeeding in any endeavor.
Set reasonable expectations for earnings. You've only invested $20. You're going to make 5 percent on most products. That means that you need to sell $400 worth of stuff to make back your investment. You get credit for purchases customers make while at Amazon besides just the product you linked to, so it's not as hard as it may sound. It won't make you rich, but it's not hard to be profitable, and the income builds over time.
Good comment Jason, at some time in the future Amazon may decide they have so much market share they don't need affiliates anyway. I mean, if you're just sending them people who are already Amazon customers there's not so much benefit there for them. Or they may decide to only work with select HIGH QUALITY affiliates and the average "affiliate site" owner will not be chosen.
Set up a website. Professional or business websites can also use the Affiliate program. However, they are best used with people who do not sell similar products on their website, since Amazon's marketplace can drive business away. If you have a website promoting different products, a club, a non-profit or a service, then you can recommend quality products on your site and make money doing it.
Freelancing is the next best thing to being paid more for your full-time work, because professional work always pays more than unskilled. To find opportunities, let former colleagues or other personal connections that you’re available for freelance gigs. (Here are some ideas on how LinkedIn could be useful for that.) Or, post on marketplaces particular to your field. For instance, Mediabistro, a journalism site, allows freelancers to post profiles of their experience and services. Though these are more up to chance, designers can bid on jobs at or submit a design at Threadless, to see if it will be crowdfunded. Elance-Odesk also lists many freelance opportunities, and you can also post your own services on Fiverr, although some freelancers say these services create a race to the bottom on fees and so are not very lucrative. If you're new to freelancing, here's how to set your rates, and here's how to negotiate raises with clients.