Start creating content on the internet. Substack, Twitter, YouTube, Instagram - whatever rocks your boat really. Post interesting content and try and build an audience of 1000+ engaged people over six months. (number varies by channel but 1000 is good yardstick for email subscribers).
If you’re leaning towards an industry, create content that you think experts in this industry would want to consume.
Once you’ve built a small audience, do user interviews with them. Ask these folks about the most parts of their work day they find most annoying. Then ask them what they’d be willing to pay for a tool that reduced time spent on doing this annoying task by 10x. If possible, make them commit to a pre-order for this tool. Give them a big introductory discount to make them commit to the pre-order. All of this will be free to you and you’ve spent $0 so far.
If you’ve gotten this far and haven’t given up, good job. Ideally you now have 5-10 orders/expressions of interest for your future SaaS product. Now go to Toptal - spend 5k on getting a full-stack developer ask him to build you a good MVP.
Congratulations, you now own your own B2B SaaS business. You’re not rich but if you stick to it you should be able to quit your job and focus on this full-time after another 12-18 months. During this time, you’ll need to keep creating content to grow that audience and increase your paid users.