When calling a teacher, what's the right number of additional duties to include in the call?

I think that really depends on other circumstances within the congregation. Perhaps sometimes no more than teaching and preparation. Perhaps other times some responsibilities such as organist, choir director, Sunday School, VBS? Perhaps, in the case of a male teacher, helping distribute Lord's Supper?
Is there a specific reason why the question has been posed?

When calling a teacher, what's the right number of additional duties to include in the call?