Pay
The sad and scary thing is that it seems that pay hasn't gone up much since my days as a CFI in the early 90's.
The most I ever made was while living out of the back of my Toyota truck. I was a renegade independent flight instructor. Airport managers all over ANC were after me. I would get paid 20$ per hour cash. I had a cessna 150 but would fly out of customer planes most often. At the end of the day I often would have $100 cash. It was a lot of money in 1991. It went to buy parts, beer and dog food.
SkyHigh