Teaching in China

I am searching for a teaching job in China and i understand that you can receive an invitation letter from your future employer only to arrive in China and discover that the name of the employer on the invitation letter is not your actual employer and that it cause you problem as the foreigner.I also understand some recruiters and schools can get you to china through the L or F visa promising to convert it to a Z visa.Is this allowed?Is there a way the embassy can help an employee verify that their employer is licensed to hire foreigners before going to China and get in trouble.I am asking all this because i understand most documents are written in Chinese?