Yes, I worked for them for over one month in Shanghai. The salary was low: 220 RMB/100 min. They only kept my first 220RMB as a deposit in case I let them down in some way, which did not worry me too much. Yes their contract really sucks, but in reality, the worst they can do is to keep your deposit (220 per student). Just make sure you take students with many hours a week (less deposit) and that you quit after collecting your salary not before, so they can not withhold it. I would try to negotiate with them a shorter contract i.e. 3 months instead of 6. You can also try to negotiate a higher rate, their margin is huge from what I heard. And yes, it is true that they will not help you with your teaching in any way (but some text books are provided).