how possible is it to get a Chinese visa in my case ?

hi i want to find out,
i have an American Girlfriend whole will be working in China in January 2014 .i am a Zambian and we want to live together during her contract she will be the main sponsor for everything while we live there. and whats the maximum duration can i be given, her contract is going to be for 2 years,she has lived there before.

thank you in advance.