You have to change your attitude 180 degrees. You sound like 99% of programmers: a techie who wants to get into business. You need to think like a businessman who uses programming to solve business needs. Do you understand the difference?

You talk about file-caching, /tmp, OSs, UI, blah blah blah; all irrelevant. You should be thinking of business needs, attracting customers, marketing, talking to potential clients within your niche. This is the important stuff.

Good luck.