I agree that if you’re looking only for monetary success, a side hustle will leave most people disappointed. Though it depends what else you hope to get out of it. For years I always made free software applications on the side, partly because I couldn’t get a software-related job but also because there were still a lot of unsolved problems that software could solve back then.

That gave me both experience and the confidence necessary to land a programming job. After that, I still made apps on the side but this time for sale. I managed to make 4 (edit: 5) figures in 3 months of my first published App Store app, but considering the time it took to develop it, less than minimum wage is about accurate. And that was my best-case.

However, I gained so much from this (and so did many of my users). Looking back at how I spent my twenties and early thirties, I would tweak it a little bit, but in a do-over I probably would have invested more time, effort and money in certain projects - not less.