Economically speaking, the current domestic middle school treatment is generally like this. Except for some big cities and some key middle schools, the treatment in some schools can even make a man unable to marry a wife. As for the industry that everyone thinks can be a tutor now, as a teacher of this subject, first of all, if your school is under great pressure, you feel that you have no time to be a tutor, especially a new teacher. Secondly, you don't want to be a tutor. This should be combined with the reputation of your school, and the parents of the students are also smart. Looking for a teacher must look at the reputation of the school and the teacher.
As for the Japanese, universities don't necessarily look at high income. It depends on the type of university and the city, but you can help others translate the materials. I really can't think of any part-time job except math tutor.
In a word, economy is one thing, what matters is what you are interested in. Middle school life is boring and endless.
for reference only