I've always thought that private tutoring is illegal in China. However, I just found this info on the US Embassy website. Apparently private tutoring is legal in China, as long as that person has a Z Visa and the employer allows for it in a written contract. I never knew this! Here's the info
"Private Teaching and Tutoring
Private teaching and tutoring are very common in China, and there is great demand for native English speakers, particularly in the larger cities. However, in order to do so legally, written consent from your full-time employer is required. If you are interested in giving private language lessons, include a stipulation in your contract allowing you to devote a certain number of hours per week to private teaching."