It depends...Are you a certified/qualified teacher with teaching experience? If so, then you can earn anywhere from 1500 to 3000 dollars a month at an international school. If not, then you'll earn much less in a language school or institute. In the latter case, it will probably not be enough to support a family.
School fees will depend on the type of school. Language schools will be much cheaper than international schools. If you choose to enroll your children in the school where you are employed, you will receive a discount that can be as much as 60% in some cases.