You will never get rich teaching English in China.

Salaries in secondary cities are fairly low. I have an acquaintance who taught primary and middle school English in Ningbo. He was paid 4000 RMB per month, had use of a small apartment, and received 1 round-trip international ticket after completing his contract.

Salaries in major cities, such as Shanghai, are slightly higher. Primary, middle, and secondary teachers make 5000 to 7000 per month, plus apartment, plus 1 ticket per year. You can earn another 1000 to 3000 by taking on private students for tutoring. Teachers at universities can make 10,000+ RMB, but the hiring criteria is extremely high. You literally need a PhD to be hired by a university.

Competition for English teaching jobs in China has increased dramatically over the last year. Desperately unemployed recent college grads (from the US, Canada, Australia, and Europe) are flooding into China looking for work because there is none in their home countries. Today it is best to have a Masters degree and a teaching certificate if you want to work in China. The financial crisis is actually starting to drive down wages for English teachers in China.