Contact someone in the city recreations department. you can prob find a website for the city's recreation department and look for contact info. email or phone call. The knox baseball league has enough interest to form 10+ teams each year, there has to be enough interest in memphis to get a football league going. In the baseball league, teams pay a fee to play, part of the fee goes to providing their own jerseys (usually just a shirt) and another part goes toward paying umpires. In a football league, you would also need jerseys (again just some type of shirt with a number on the back), flags/belts, and officials. Just don't go after SEC officials....
this is the website for the city adult recreation eagues, along with address and telephone number and some info on starting leagues.
Park Services - Adult Athletics