There are two different kinds of entrepreneurs in this world: those who start a business to do what they love, and those who start a business to make money. There is, of course, some overlap here--those who start a business based on their hobby or passion generally want to make a decent buck, and those who start a business based on profit potential want to enjoy what they're doing. But there's no doubt about it: The ones who base their businesses on their passion are generally not in this entrepreneurial game for the money.
This brings us to a key question you need to ask yourself as you prepare to start a business: Are you doing it for love or money? Your answer to this question will help you determine how to proceed with your business. If your answer is "love," and you know you'd like nothing more than to earn some extra cash doing the thing you do best, then starting your business will be slightly simpler than venturing into a business where you're hoping to make a million your first year.
And I don't mean "simpler" because you'll have less work to do--I mean "simpler" in the sense that you won't be hung up on a dollar figure. Instead, you'll be pouring your heart into something that you'd likely be doing with or without any monetary compensation involved. In my opinion, this is the best way to start a business. Think of it this way: On those days when you're at the end of your rope and you think there's no possible way you'll see the break of dawn before you keel over in exhaustion, what would you rather be doing--something you enjoy, or something you have to do to make ends meet?
I know there are plenty of people who start their businesses solely with the intention of making money and perhaps selling the business later. If that's what you want, go for it. But if your goal is to really sink your teeth into the idea of being an entrepreneur, do some soul-searching before you start a business.