If you are good, you will have a comfortable living as a tennis instructor, but by no means "wealthy". There is a tennis instructor around here that tries to work almost 12 hours a day, all year, and gets paid $35-$40 an hour. You can calculate out how much he potentially makes from those numbers.
Another coach around here gets paid to have a successful collegiate team, and he is comfortable - if not very wealthy.
You will have to become a "star coach" to get the big money.
If you donít practice you donít deserve to win.