It all depends where you are going to sell your products. If you want to sell say in New York City you need to get permission to set up a shop or a vendors cart.

If you have an apartment and you want to sell hats you could do that without permission in some places and not in others, it all depends on the zoning rules. Just call the city that you plan to be in when you make your sales and ask if you need special permission or not, they will tell you without asking who you are.

If you had a friend who already had a commercial space they could let you sell in that space and you would only need to be concerned with city and state sales taxes and of course the IRS.