If you know English well enough, you can theoretically teach English at any age. You can get involved in TEFL‏‎ (Teaching English as a Foreign Language) or TESOL (Teaching English as a Second Language) whenever you want.

On the ICAL TEFL Certificate Course, for example, we have had students from 16 to well into their 80s! But after the course, once the teacher is trained, how easy is it for a…