If you’re a student and are looking to make some passive income in the new academic year, try [BuyNotes.co.uk](http://buynotes.co.uk/). You can make a reasonable amount of money selling notes you make anyway during your studies.
If you’re no longer a student but still have any study materials you made during school and upwards you can sell these also.
In addition to this, if you run a relevant blog or other relevant outlet you can apply to become an affiliate of the site and receive revenue from users who sign up using your code. You can do that at [https://www.buynotes.co.uk/affiliates/apply/](https://www.buynotes.co.uk/affiliates/apply/) . Further information can be found on the FAQ page.
Disclaimer: I am one of the creators of this site and would be more than happy to answer any questions! The site is currently UK-centric but international users can still upload and sell products if they wish.