- How are you going to make money? What if that revenue model doesn't bear fruit... any other ideas?
- How are you going to reach your customers? How much will it cost to reach your customers?
- Roughly, how big is your market? Is there a lot of demand?
- How big a team do you need to test your initial theories and roughly how expensive is that going to be?
- Are there any other significant expenses aside from people?
- How many sales/pageviews/whatever would it take for you to be cash flow positive?
I don't good investors ask these questions to test your planning powers... I think they ask them to test how smart you are and how much you've thought about this stuff.