My family and I have two unofficial businesses, and we're wondering how difficult it is to get an actual website going.

I know that we have to have a Business License, making the businesses official, in Ohio.

But what i'm curious about is how the whole system works.
Like the payments, inventory, and other things involved in the whole "Shopping" part of the site.

I know enough HTML and CSS to make a website look good. But i have no idea about web programming involved with selling online.
I have made many, sites that are used for advertisements, or location/contacts