County income tax on self employed

[tvvcoch]

Georgia, Gwinnett County. When I was laid off, I started consulting. I have a home office but my consulting is at the customer's location generally. I also have a mail order business that I take on the road to festivals. Now, Gwinnett County is charging a "home occupancy tax" on those claiming a home office on tax records and business income. They also impose a type of income tax. Isn't this illegal for a county to do this? I already collect sales tax and pay that, pay state tax and federal tax. Isn't that enough tax from someone who fights daily to keep the house I live in?