Actually it should have been stipulated in your lease. Typically the leasee is required to carry liability insurance and that policy should cover the leaser as well as himself. If he didn't raise the point I would still get it, as it is the only protection you have for your personal assets. Even if you are incorporated, a lack of corporate assets allows for the corporate veil to be pierced and the indivuals to be held liable. Your landlord's insurace will protect him, but it will not cover you.
Pricing on policies typically depends on things like number of students, do they wear protective gear, do you do full contact, do you spar, do you teach weapons, etc.
A lot of schools make their students pay for their own policy when they join. Just something to consider.
