The right time to teach piano depends on you. If you are confident enough to let your skills out, then that will serve as an ideal time. The way you teach your students also plays a detrimental role. Just by producing some pieces of paper to show that you are a piano professional, it’s not going to work. People should see the results straight away. Therefore, you need to be well prepared to teach your students some easy lessons to start with. Students may get nervous initially. Give them some time, and do not make the mistake of teaching in a theoretical manner. Always begin with easy notes so that students can feel comfortable learning at the start.
Teach from memory initially. Make it a point to teach bit by big, showing them the keys to hit, so they could grasp things easily. After a weeks class, make them reciprocate the same, so you could get to know if the student has really known something or not. The best way to progress is to analyze the student’s difficulty, spending time with her and work on small parts. This will give you self-satisfaction for having taught a newbie on how to learn piano.