How to monetize a job board for teachers?

I decided to work on a job board for private teachers as in my country job boards for teachers contain very few teachers, rarely updated and are all paid (students pay to contact a teacher).

I know a lot of teachers and started building a directory. I believe that I can become the biggest directory in my country within a couple of months of community building.

I hate the idea of students paying to contact a teacher. I wouldn’t use this service as a student.

How should I monetize?

I’m interested to find similar examples.

Thanks!