I started building Requestly (https://requestly.io) as a side-project back in 2014 and It took me pretty much every Saturday for 7y to hit ~$2K revenue and to get few companies paying for the product. It was slightly hard to monetize chrome extension due to lack of payments APIs support in chrome ecosystem. I actually went full time in Sep'21 and was fortunate enough to get into YC(W22). Now we are a small team based in India building Requestly.

Requestly is an open-source [1] Chrome & Firefox extension [2] that I started to help me in faster web development by capturing & modifying network requests directly in the browser without using any external tools. It eventually replaced Charles & Fiddler for many companies but now we are building a desktop version[3] too.

On a side note, Side Projects are a long-term game but the good part is you can do multiple along with your job and pick the one getting more traction. For example - I did many other side projects but continued with Requestly for 2 reasons - I was using it myself almost everyday and It was gaining organic traction.

Good luck in finding the project of your calling.

[1]: https://github.com/requestly/requestly

[2]: https://chrome.google.com/webstore/detail/requestly-redirect...

[3]: https://requestly.io/desktop