The Skype pipe dream
A good Vocal Coach is not only equipped with a good ear, which will appear obvious to all, but also a great sense of observation combined with a great capacity to communicate.
This is the main reason why I do consider that teaching over the internet through Skype or another means in not as good to be in front of your teacher. Nowadays, the average quality of the current technology available to users is way too low and special hardware must be seeken for offering a service that is ethically correct and fair to the student.
The purpose of vocal training is to initially return the voice to its naturalness, removing all the muscle tension unconsciously introduced into the body preventing the vocal expressiveness which we are given. How you can help a student during this important step if you have no way to evaluate all these items?
If the technical part is not good enough, it is like giving up to 80% of your Vocal Coach, while paying them in full.