You will want a federal taxpayer ID.
You need to decide what type of business you will want to start, Sole/Partner/LLC. Will you incorporate?
Develop a Business model or plan. Draft up an exit strategy. If you plan to succeed do your homework now to be prepared for the future.
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The costs will differ due to what type of business you decide on. In my state they charge a different amount based on type of business, what you will be doing, and where you will be doing it. The total start up cost depends on who, what and where, so the price cannot be easily figured out. But you should be able to get some sort of license for a couple hundred dollars.
The type of business will most likely affect tax rate as well. Make sure you keep about 40% of the profit off to the side for state tax, federal tax, Social Security, Medicare. Remember that your obligation to Social Security will be the full amount.
Learn a little about accounting so you can learn to keep good track of your money and expenses.
