You should form an LLC or corp of some kind NOW. One thing most people forget when they are setting up a small or home based business is Personal Liability. If you're running a business in your name and something goes wrong, YOU get sued. If you've got an LLC, structured properly, and something goes wrong, the LLC gets sued. It will sheild you, and your assets. So I wouldn't wait. Plus you want something in place for taxes before you start making money, not after.