We are staying with friends that live in Beijing, as we won't be at a hotel, what info is needed?

You need to provide an invitation letter from your friends, which include:
(1) Information on the applicant (full name, gender, date of birth, etc.)
(2) Information on the planned visit (arrival and departure dates, place(s) to be visited, etc.)
(3) Information on the inviting entity or individual (name, contact telephone number, address, signature of the inviting individual)