As someone with many failed side projects, I can tell you that having a goal of making money is usually a bad thing. Like many other people have said, you can l

As someone with many failed side projects, I can tell you that having a goal of making money is usually a bad thing. Like many other people have said, you can learn the skills. The hardest part of building a side project is finding the time and staying motivated for more than a few months. So, pick something _you_ will use and, if you enjoy building/using it, so will others. Obviously think about ways to monetize it, but money should be more of a side-effect than a motivation. I'm currently working on https://insomnia.rest https://insomnia.rest, which makes around $800/mo right now. I started it as a side-project a couple years ago with no intention of making money. However, traffic grew organically and I eventually left my job to pursue it full-time. In summary, find something you love to work on and let it consume you. If you do this, making $100/mo should come in no time. Have fun hacking!