Personally, putting aside e-commerce transactions (ebay etc), I did my first dollar on the internet by promoting Udemy courses on a blog I created yeaaars ago: http://elearnhero.com/. So the very first time I made money online was through affiliate marketing !
I put my Psychology notes and book summaries from some of my Bachelor degree courses on an online platform for students. It's not as frequent now but I still get a few sales before the exams start!
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