First, you should read carefully about the salary that is before tax or after tax. Most of them are before tax. Then, you may want to figure out the tax rate of your salary and money you get after tax.
Second, sometimes the schools will provide housing allowance instead of free apartment to you. Then, whether the housing allowance is deductible or not should be figured out. And you may also want to know the free apartment that is a shared or not.
Third, you may want to the fee of applying for the work visa. Does the school cover it or you need to pay by yourself.
Fourth, there are many famous language training center chains in China. Sometimes, it’s said you may be transferred to other branches for a while during your contract. You may need to get clear about that if you just want to stay at the city you are applying for.
Finally, remember to read every word about the contract carefully and get to know it. If there is anything that makes you confused, please contact with school or your agency to make everything clear.