Part time works if your idea is realistic for part time. Is it easy to implement, easy to scale? Does it have a core of good functionality?

I recommend reading 4-Hour Work Week by Tim Ferris. You need a strong hype/BS filter, but he has some good suggestions about time management. In particular, there is a chapter about how to reduce the number of hours you have to put in at your day job without reducing your effectiveness. For example, if you work from home, you reduce interruptions and meetings. He tells how introduce telecommuting without your boss realizing what is happening.