I think side projects and businesses are a great way to learn and have an interesting life, so I am usually doing something outside of work. My friends write plays and do standup which sometimes pays. I used to teach swimming after work because it got me to the gym and I could develop my communication skills.

Currently, I have a hobby map business that generates some money (https://www.wellingtonstravel.com/). Recently I created a matchmaking app for people who travel. It's not making money yet, but I expect it to be able to generate income too (https://www.fairytrail.app/).

I believe it's about finding what interests you first. Money is a nice bonus.