Every entrepreneur "believes" that his/her project has the potential to make money. They're probably even right that it has "potential". But you can't pay the bills with "potential".
My question(s) would be: Have you done any market research? Have you talked to the prospective customers for this thing? Do you have any low-cost way of validating your gut-feeling about the demand for what you're building?
I don't want to sound like Debbie Downer, but it would be tragic to burn a pile of time and energy building something and then find out that there's actually no market for it. Or, that there is a market, but that it's not large enough to sustain a business in the long-term. Or that there is a market, but that you can't serve it profitably.
I'd try to make sure I had this stuff nailed before even getting into the equity splits and profit sharing discussions with your friends.