Wow. You have the same questions everyone has when they first make that decision to take a risk. I'm in the same boat myself, and my only guess would be to look at all the successfull people in the world, and know that most of them had the same questions. So, I bet all we have to do is move foward, be persistant, believe in what you do, and the rest will follow.
Good luck, and Go for IT!
And hopefully we'll see eachother at the top!
"If one advances confidently in the direction of
his dreams, and endeavors to live the life he
has imagined, he will meet with a success
unexpected in common hours."
- H.D. Thoreau