You already know what’s broken
No matter what you do for work, you have insight into a problem (or several).
You probably understand the market, the customers and the issues your employer is facing. You have inside knowledge into a business and, that’s worth something.
I learned how hard it was for large enterprises to deliver software, how little music stores cared about customer feedback and how easy it was to steal from security guards in previous positions.
You might not know what the solution to the problem is (yet) but, you already know what’s broken in the industry you work in. If you’re passionate about solving that problem, you might be ready to start a business.
Inside knowledge and deep industry understanding are at the root of the successes of many businesses (Fast Company, Salesforce, Zappos, etc).