I was watching Jet Li's fearless. One thing is in the movie he took on students whoever asked. His students almost backrupted him. Then they got him in a fight with another teacher, whom he killed. Later it was found out the guy was sleeping with the other school's teacher's mistress.

People would say this is a business. However, as sun-tzu said "it is foolish to let fate decide your troops." One thing is in martial arts school your students are the people who will get you more students, buy stuff, and help out with things.