If you find a customer, and find a solution, and make a tentative sale, don't go wander off and do something else. An otherwise bright young lady I worked with last year has all three things: problem, solution, and customers. She's going off this summer to intern at Deloitte instead of building her business, because she "wants to learn more about business".
You know what else teaches you about business? Running a fucking business.
Presented with this fact, she said she wanted to learn more about the "strategic side of things...mergers, acquisitions, aquihires, etc.". Those are all issues that are pretty far off if you're just starting out as a business, and you won't likely worry about them until you are big enough to care. And if you're expecting to worry about them at another company, you are going to be hired in as a junior employee anyways so you won't even have anything useful to say on the topic.
The tech guy on that team is trying to find tech jobs at other startups--again, despite having a problem, a solution, and customers.
I've sold apps and had customers, but not at the scale that would let me quit my day job.