It's better u stay in China.Some Chinese people i know here are not happy cos there is hardly any form of entertainment.If your would-be employer can't provide for your airfare,it's better you forget the job.Paying your airfare shows they are committed and reputable.
All in all,don't negotiate for less than USD1500/month with free accomodation,airfare,medicals,transportation and holiday pay.
Just to let u know, a Chinese friend of mine who works as a Chinese/English interpreter gets USD2000/month on top of other perks.
All the best.