In my consulting career, I've been fortunate to see similar problems multiple times -- hopefully, I'll learn from each one and not make the same mistakes the next time I encounter that particular situation. One situation in particular involves a conversation with an entrepreneur, and it goes something like this :
Entrepreneur: I have an idea for a web app that will revolutionize the [blank] industry, and make us bajillions!
me: That's great! I can tell you are passionate and excited, and that's critical to your success. But do you have enough cash to pay for this coffee?
Entrepreneur: Yes, we have some funding to get started. And I have a business plan explaining our strategy, and I have a powerpoint deck of what the product does.
Me: That's even better! I'll have another espresso then.
Entrepreneur: We'd like you to get us started on our website development. Here's our feature set for beta release. How long is this going to take? How many people, and what other stuff do we need?
Me: Ummm....and that's where the conversation gets difficult. Because the business plan doesn't go into great detail about the product (it shouldn't), and the powerpoint slides have a bunch ...