Which type of visa i should apply?

You need to apply for a business F type with the invitation letter from your friend.

Basically he does not do any business in China, he is 21 years old student. Kindly advise?

What is your purpose of visit? as I know, Pakistani passport holders can not apply for individual tourist L, so your friend may not be able to help you on this. You have to join a tour and apply for a group tourist L with an invitation letter from a China travel agency.

Yes Tommy you are right! I am basically going to meet few friends on mine in China but dont want to join a tourist group :)
I want to backpack and travel around myself, therefore hoping to get a solution.

Sorry, I am afraid you can only get a group tourist L with an invitation letter from a travel agency.

Thanks Tommy! Yup it seems that the only option!