Their policies are strict. Be sure to read through Amazon’s affiliate program policies very carefully. Any violation of their policies is grounds for account suspension--something which could be devastating if you build an entire website or store around affiliate links. Amazon has also been known to suspend accounts without any prior notice, so tread carefully.
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 have a propensity for writing and you can slay with your prose, consider writing an ebook. While the market has certainly become saturated as of late, books that help teach people about a technical topic still sell extremely well. This is a great source of passive income but does require a large amount of effort at the outset before any money is generated.
Affiliate marketing is an ideal solution for those looking to gain control of their own income by focusing on performance-based revenue options. Working in tandem with a seller, a motivated affiliate marketer will be able to achieve a passive income from the comfort of their home without worrying about producing their own product or service. Although the success of the job does depend on the affiliate’s marketing skills, it can prove to be an effective way to meet your income goals as either a primary career or a profitable second job.