Clearly, there's a lot of demand on Amazon, and if any product is going to sell, it's going to sell well on Amazon. But the goal here is to source the right products that will easily sell at the world's largest online retailer. Generally, products between $10 and $50 sell very well here. Just be sure to do the right market research before jumping on this bandwagon.
You can sell your ebooks through Amazon's Kindle program or Apple's iTunes Connect, which gives you access to a large majority of the digital-book reading market and the barriers for entry are incredibly low. You don't need to invest lots of money to make this happen, but you do need to invest lots of time, not only in writing the ebooks, but in marketing them as well.
If you’re looking for inspiration, my friend Michelle Schroeder-Gardner of the website Making Sense of Sense has become the expert on all things affiliate marketing. Michelle earns more than $100,000 per month from her blog and the bulk of her income comes from affiliate sales. Michelle has had so much success with affiliate marketing that she even has her own course called Making Sense of Affiliate Marketing.