7) Are you passionate about this? Does it keep you up at night? Because if the answer to either question is no, I'd reconsider. You are going to have to sink your whole being into this business for a long time to make it work, unless you are satisfied with doing it as a hobby. If it isn't haunting your dreams, don't do it.
8) Go talk to an accountant. You can get a free consultation about how much money to save for taxes (25%. That's right.), when you will have to pay estimated taxes, what is deductible, what isn't, how to set up your business accounts, how to pay yourself (I have a business account. Every dime I make goes into that account first. Then, I put 25% of every dime into savings. Immediately. That money isn't even mine anyway. It belongs to Uncle Sam. Then, I pay myself a salary out of that business account every month by transferring money into my personal account on the last day of the month. And I do. Not. Cheat. I get paid what I get paid. Because if I dip into it? I don't get paid next month. But I included in my estimate for my salary things like health insurance, which my employer *should* pay for. Also, if I am going on a business trip, I take the cash for that trip out of the business account.) The accountant can also tell you about LLCs, corporations, and a business license.
9) Get a business credit card. Do as I say, not as I do. I don't have one of these yet. I just print out the balances for the year every year and go through it with my highlighter, noting my business expenses (which are usually trips).
10) Just do it. I was going to wait before contacting potential clients until I had a professional website in place. But our very own Kathy Howe told me, "You have a finger and a phone. Start dialing. You don't need a website. Get off your arse and do it." So I did. And I have been doing it ever since.
I will add this caveat: The week before I took the plunge, I received a potential client list in the mail from a professional organization I belong to. So, I got some nice quotes from my existing clients, and wrote an introductory marketing email and begain sending it out to everyone on that list. I got virtually every client I have today that way. Eventually, someone complained to the organization about spam, and they very nicely asked me to stop doing that. So, I very nicely stopped. Now, I go to the conference every year and rent an exhibit table, and give workshops when I can, and network that way.