Welcome to the Forum. There is a lot of great information here.
Please don't think of what you are doing as a hobby. You are running a small, part-time business. As a business you have revenue and expenses and will report both to the IRS on Schedule C. If you insist that it is a hobby, you will report the revenue to the IRS, but you can't deduct expenses. You will pay more taxes. You WILL have expenses.
I have been retired for about a year and a half and decided to give Mystery Shopping a try as something to do (hobby). Dont know how it will go but hoping to have fun.
Shopping Southeast Pennsylvania, Delaware above the canal, and southwestern NJ since 2008