I think a better solution than a side hustle, is to gather your friends or coworkers to propose to create, collectively, a worker owned co-op (of whatever idea seems profitable).
As it's being done collectively, there's more of a chance of it getting off the ground, as people could take turns working on it in their spare time instead of a side-hustle dominating your time.
Once it's established, those people could then quit their job and work at the coop.
There are credit unions that could help with startup costs, as well as guides on how to structure it based on other successful coops.
I am a big fan of alternative ownership/governance structures in businesses, and this approach might work.
Potential issues: employers don't tend to like it if they get wind that a group of employees are doing something on the side, and may find reason to take ownership of said effort (which your contract might allow them to do).
As it's being done collectively, there's more of a chance of it getting off the ground, as people could take turns working on it in their spare time instead of a side-hustle dominating your time.
Once it's established, those people could then quit their job and work at the coop.
There are credit unions that could help with startup costs, as well as guides on how to structure it based on other successful coops.