Try this - http://www.thebeijinger.com/
A lot of Chinese guys there looking for teachers. But you can't always trust Chinese people, so I would use StretchPay while giving lesson.
Good luck
It's not easy to find students when you just start, coz online teaching is a new stream and needs a certain level of trust as well... You can place add on Gumtree or smth like that and just trust your students (they usually dont prepay for lessons). To make sure you'll be paid for your time you'd be...