I could do this in my 20s and before I had a family but I've realized that it has become increasingly hard for me lately to manage everything especially raising a family. I'd like to spend time daily with my kids and don't want to pull 40+ hour work weeks anymore.
I feel like a sustainable pace would be working 3-4 hours a day and building something. I love building things so that always excites me but I'm not so excited/challenged by the people aspect of a job where you are required to be influential across orgs especially in as a Senior engineer in BigTech.
Anyway, all of this is just context for what I've been thinking since long: to quit my BigTech job and build something of my own on the side that generates just enough income for me to sustain and help raise my family. I'm at a stage financially where I have some cushion but not enough to be fully FIRE'd so I will need some income to sustain mortgage + kids + lifestyle.
Where do I start? What ideas do I explore? If any of you did it, what was your experience like?
Bootstrapping your own thing will give you more of that, not less. It takes an established business to be stabile to the point where the surprises are minimal, the processes are standardized, and the team is built to absorb whatever is thrown at it to handle things without putting in extra hours.
It sounds like you need to find established companies who need some part-time help.