Are you planning on being a CFI forever? I think you're wildly shortsighted if you thing the roi is small because your first job sucks. That's the case for everything from apprentice in a trade to a doctor.You make nothing, spend your professional life in rental aircraft that are generally in deplorable condition, and have to constantly stay on the lookout for ways your students will try to kill you. That is the lifestyle you get for your ~90K investment.
It's fun and rewarding teaching people to fly for sure. Truly, interacting with students is great and it's awesome to see them achieve their goals. But man, the return on investment is... small.
Might consider a different field if you can't handle the day to day of a CFI.