Sell your notes
If you don’t mind sharing your notes with other students it’s a great way to generate a little extra cash. There are sites out there that you can upload your notes to, along with your price, and then when another student downloads them you get paid.
Most of these sites like Stuvia & Notesale are free for you to list your notes but tend to take a cut of your profit in order to handle the marketing etc so that you don’t have to go out there and promote your notes yourself.
You will most likely have to upload PDFs but it’s worth it for the return and you can submit handwritten notes but you’re likely to make more money if they’re typed up.