– Project Payday is one of those sites that has testimonials of people who have earned thousands of dollars by getting paid to get trial offers. I’m not saying you’ll earn thousands, but it is legit and you can earn some extra cash. They assume that by paying you to do a free trial, you’ll either like the product and purchase it, or forget to cancel the trial and get charged for it. If you can keep track and cancel before you get charged (if you don’t want the product), then this is a great site for making some money.
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.