I know a lot of photographers here in Texas that don't charge tax for their services. I was in a computer business once where we did freelance computer builds and repairs, networking, etc. Each of us got our own tax ID number from the state so that we could charge tax on what we were selling. The way it's setup is you choose when you pay the tax owed to the government.(monthly, quarterly, bi-yearly, end of year, etc.) Then you pay the government the tax that you had charged during that time.
^----That's all I know about if you were going to add tax to your work. Like I said though, none of the photographers I know charge tax since they sell it as a service(like a landscaper does).
Income tax is a different story. You're "required" to pay in on Income Tax, Social Security, etc. on money you make. Just like at any other job, when you get a paycheck, the taxes are taken out of it...so if you started your own business, you still are "required" to pay taxes on what you make. I have no clue on what's involved in setting that up.