Don't get caught with the wrong visa or it will cost you an arrest, a $2,000 fine and a deportation friends. As of September of 2013, the visa requirements to work or teach in China have become quite strict. The enforcement of these visa laws has become even more strict. Gone are the days when you could work on a tourist or business visa (L and F visas) and just pay $1,000 to a PSB officer if you were caught. Today everything in China is by the book as we just saw in 2014 with over 1,500 expat teachers being arrested, jailed, fined, and then deported for working without a work visa (Z visa).
There are plenty of recruiters and visa agents who may talk you into working as an intern or tell you that L, F, and M visas are okay for working during your first "90 day probationary period". This is not true. The Chinese visa law specifically says that you MUST hold a Z visa to work even part time in China from your very first work day. There are no provisions to do otherwise without getting yourself classified as an "illegal alien". People still try but half of them get caught within three months.
So let's keep it simple here... to LEGALLY work in China, in any profession, you must land in China with a Z visa. If however you originally came to China as a student or a tourist and then decided you want to remain and work in China, you must leave China to apply for a Z visa outside of the country. Most people will fly to Hong Kong to meet this requirement.
To get the Z visa, you need to have your prospective employer send you an original invitation letter on their company letterhead that is signed, dated, and chopped (corporate seal) clearly stating that you are coming to China to work as a teacher on a ______mo/year contract and this letter should specifically request a "work visa".
Having said this, things change in China all the time, so if there are any changes we will update this thread. If you do not live within 100 miles of a Chinese embassy or consulate you may opt to use a visa agent, but caution is urged. Use only well known visa agents with a proven history and legitimate office address and website that is more than one year old. You can even ask the Chinese embassy or consulate "Do you accept applications through visa agent __________"
There are many other visas issued by China for cultural exchanges, business training, university students, etc. - even a new 10 year visa for American business people. This thread talk about the only acceptable visa needed to teach in China - the Z Visa.
If you doubt any of the above, just contact the nearest Chinese embassy or consulate or visit www.SAFEA.gov.cn