With budgeting issues in education today, the HARDEST part about being a music teacher would be finding and securing a position. Many schools throughout the country are losing their music programs due to a lack of funding. I am not stating this to discourage you, but to ensure that you consider other options, such as giving private lessons, or as an after school program.
On the other hand, the BEST part about teaching music is how rewarding it will be to teach a student a life-long skill....as well as to sit back and "hear" the benefits of your labor. The ability to play a musical instrument can be life-changing!!
Good luck with your "musical" endeavors!!