This is the first installment in a three-part series. Part Two will explore how you should go about gaining the knowledge and certification you'll need to become a highly qualified pro. Part Three will weigh some of the pros and cons of life as a tennis teacher.
It's often been said that the way to choose a profession is to find something you love to do, then find a way to get paid for doing it. I don't know how many of us manage to work things out that well, but I would guess that people who teach tennis for a living have found their true calling to a greater extent than most. Like any profession, teaching tennis has its difficulties, but there's much to be said for being in a business that's largely focused on helping people have fun.
If you think you might want to become a teaching pro, your first step should be to become an experienced and well-rounded player. For example, you might be able to beat everyone in your town without ever venturing to the net, but if you're going to teach others who might not have your baseline groundstroking talents, you need to know how to play the net. A good tennis teacher should know not only his or her own game, but how to play with a wide variety of styles. You shouldn't be forcing students to model the one playing style you prefer; you should be able to help them find the style that suits them best.
For the sake of your students, you should also do some serious studying before you start. Gifted players don't necessarily make good teachers. What comes naturally to you might be difficult for someone else, and if you don't have a thorough understanding of a wide range of strokes and how and why they work, you'll end up offering your students little more than an opportunity to try to imitate your style of play. Worse, you're likely to perpetuate many of the myths that abound in the tennis world.
One way to develop a deep understanding of the game and its teaching is to take lessons from the type of pro who will encourage you to learn a wide range of strokes and to apply an analytical approach to improving your own game. You can also explicitly hire a pro to teach you how to teach. If a pro is unavailable or unaffordable, you should carefully study at least two comprehensive and detailed books on tennis. This amount of study is merely a minimum preparation for a beginning job. You'll be studying in far greater depth as you prepare to become a top professional.