Yes, it is necessary to book hotel in advance. It is better book one month in advance. There is some budget accommodation in Guangzhou which is those called “white collar apartment”.
Many of these apartments are available to rent on daily, monthly or annual basis.
The facilities varies according to different apartment, with some of them claim themselves up to 4 star hotel standard, vs. those which is just low end apartment.
Usually, 3 people can share one apartment, more information about apartment pls. check:
http://www.ecomeego.com/Accommodation/White%20Collar%20Apartment.html