How Much?
China is cheap! You can find beer for 16p, eat meals that cost under a pound (beer included) and buy clothes, get £5 massages and get CDs and DVDs for roughly 50p-£1.
Difficulties
The standard of English speaking in China is very poor and although it is improving it is useful to get a phrasebook (with Chinese Characters).
Chinese food is amazing (and nothing like takeaway in England). However, it is quite difficult to order in restaurants without menus in English. Get Chinese recommendations on what to eat or just point at other people’s food in restaurants.