Starting up a small business is very easy in most cases especially if the small business operates mainly online and you don't have customers coming over.
If it's just you and maybe someone else working out of the home on the small business then you likely can get by for awhile even without getting licenses etc.
However if you have customers coming over then you will most likely need a license to conduct business out of your home and should check with your local municipality.
I actually run an ebay store from home and I don't even have a license because it's just me and my sister working for the business.
I started the business 4 years ago and sell stuff I buy through Costco at a discount and then resell for profit and I do make some good income per month doing so.
I take the orders and she packages and ships the orders to the customers.
Online businesses can usually be started just fine out of your home without licenses but as you get more income and branch out it can be a good idea to get a business license anyway as they're very cheap and make you look more professional especially if you plan to open your own online store without using ebay.
I also have a dedicated home office and a dedicated computer I use solely for taking the ebay orders and a separate personal computer I use for browsing the internet that isn't in my home office that way I separate work from home life.
It makes me more productive and organized and at the end of the day I shut and lock the office door and don't go back in there until the next workday unless I really need to do something in their.