Oh yeah, I totally support having a fixed income while building a side project. Otherwise it's too much stress. When you're alone, fine, you can get your monthly expenses to minimum and say to yourself: "ok, i'll try this thing out, i think it's a great idea, i'll focus on it for a year, i live more simply so i wouldn't need that much money, let's see what happens"
But when you have a family, it's a different game. This is where, I think, calmfund.com etc can be very helpful (although they usually want to see some MRR I think).
HostiFi had a good $3k MRR when the founder got fired. And I think reaching the initial $3k or $5k is so important because it shows that people are willing to pay for your product.
But the other startup Bannerbear actually didn't have a decent revenue, making only $234 MRR. The founder contributes the MRR growth to a mindset change:
"I think that mental switch was important. Getting a job was no longer an option, it was Bannerbear or bust."
Been there, totally agree. It also makes you think things through less introducing sloppiness, cuts corners introducing bugs, spikes stress aggravating the situation, causing near certainty to miss the final deadline.
I'm the 2nd example in the post (Bannerbear.com) and I wasn't in a full time job when I started it. There was definitely a feeling of existential motivation...
Trying to turn a project with 0 revenue into something, while having no fixed income is most likely going to fail, and ruin you in all sorts of ways.