Is it legal to work in an language school with a business visa or working visa?

I'm in Dongguan, in Guangdong province right now, trying to find a way to work (as a english teacher) or stay here in China legally.
From the info i find on the internet and asking around, I think that working with a business visa for a langauge school in china is illegal. is it true? or is there an exception to it?
Or is it legal for me to work for the language school as an intern (not paid but still get food and accomodation) with an business visa? and is there a condition or requirement for me to be an intern such as having a bachelor's degree or whatever?
thank you