If you're starting an online store, here's what you should do:
- Talk to your local government in your city and see if you need a business license
- Register an LLC with the state
- Set up an EIN with the federal goverment
- Spend $500 and get an attorney to give you his/her blessing and make sure you have the necessary terms of service documents and any contracts you'll need.
Make your first $500, and prove your ideas worth it, and then do all that stuff and pay any fines and/or taxes you need to pay to make it right.
If your business doesn't go as planned, you saved time and money.