In the world of contemporary music, there are no prerequisites for being a singing teacher or coach. Many of the most successful professors I know don't have college degrees. However, they have a wealth of training and experience. You don't need a degree to play or teach music.
Either you are already a solo singer or you have experience singing in choirs. Hopefully, you also have some ability on the piano, because without that ability you will be disabled. Professional vocal coach John Henny points out that voice teachers and vocal coaches have different roles in the music profession. If you hire a teacher or coach, look for one that uses a teaching system that allows him to achieve vocal balance, advises the Institute for Vocal Advancement.
Good vocal coaches possess the engaging combination of a great singing voice, an understanding of music, and the ability to teach and inspire others to master their voice. A good voice teacher is able to transmit this knowledge of vocal balance to his students in a way that works for each individual voice, applying the best vocal skills and techniques to songs of any style or genre. I was recently asked to teach singing lessons to a six-year-old girl who has been taking singing lessons for a while, but I haven't received any formal training for this.