I think it is hard for you to get a multiple entry visa valid for 6 months, The applicant may apply for a multiple-entry L visa, if his/her spouse, children, or parents are Chinese citizens, and he/she presents related certificates on relationship or invitation from relatives in China, or if he/she possesses real estate in China, and presents the original and one photocopy of the registration certificate for ownership under his/her name, or all the other documents to show the necessity for this kind of visa. Even you get it, you can't stay in China for 6 months continuously. You have to exit Mainland China when the each stay is up.

You should submit the following documents for Chinese tourist visa application:
1. Visa Application Form, which must be earnestly filled in and signed by the applicant
2. Original passport with blank visa pages, valid for more than six months, copy of the information pages of the applicant's passport
3. one passport photo to be to be affixed to the application form
4. Invitation letter from the your friend, copy of his passport, Chinese visa, residence permit