Not enough as far as I can see - they should be paying you much more
Singers are quite capable of teaching each others to sing if they work it out between a group of themselves without having to pay a stranger who almost certainly doesn't know as much about the songs you want to sing as you do
I've tried often enough to discuss relaxation, voice and singing exercises devised and developed by some of te UK's finest singers....
Your money, of course
Jim Caarroll