What is the average yearly income of a sign language teacher?

Depends on where you teach. If you are teaching American Sign Language for a college or university, you will make what typical professors make at that particular school. Between $30,000 - $50,000 to start.

If you are teaching for a community college, community center, etc the pay would be lower, of course.

If you are teaching ASL as your own business, then sky's the limit. :-)

Good luck!