Several ways to look at this. If the person is a good teacher and has a positive influence on students and their futures, I hope the person would keep teaching.

I had the same struggle from 1968 to 2004 when I retired from teaching. I was in business for myself while in college and had to get out of it when I started teaching. My first teaching contract was less than what I made working for myself, but the intrinsic income from teaching was great. All the time I was teaching, I was in business for myself also.

I retired from teaching in 2004 and now I'm working seven days a week in my own business. I'm enjoying it, but I don't regret teaching. I have yet to have any customers from my decades of being in business look me up and say they really appreciated me being there for them so they could buy whatever my business happened to be. On the other hand, I've had a number of students contact me and say thanks after all the years.

When I was doing graduate work, a professor told a class I was in that many teachers thought about things backwards. He said they were trying to find a way to make enough money to quit teaching. His advice was that they should be trying to find a way to make enough money that they could continue teaching. I bought into that theory and never regreted it.