https://www.startupschool.org/ might also be relevant, free to consume.

Or, work & work over time on your thing. It'll take longer then, if course, but if it solves an isolated problem - I don't think you'll get much competitors. As long no one knows what you're solving..

I tried to do something while being on regular 9-5-5 job - it's a big big pain and slow as f*. But then I got fired/laid off. Now I'm wasting my time without earning money, as doing my idea doesn't really advance. But some day... Some day...

So, check if you can do everything in your leasure time. If yes, keep your job for money. If money is enough, quit and build. Or, may be you're lucky as me and get laid off..

Keep building your future.