Most apartments in Beijing come "fully furnished," which means you won't have to buy a bed, a couch, tables and chairs, etc. However, don't forget to factor in the cost of housing supplies and bedding!
When I taught English in the Chinese countryside three years ago, my company purchased all of these items for me. I now know I was a bit spoiled in that regard, and many fully-furnished apartments come with a hot plate and nothing else.
I wasn't prepared to buy my own bedding, cups, plates, pots, and pans for the first month. While I decided to skimp on a lot of cooking supplies, I did need a pillow, sheets, a water boiler, and a cup! While these items are cheap, they all add up if you haven't budgeted for them.
How to Avoid This:
If you're provided an apartment as part of your contract, be sure to ask what your apartment will come with so you know how to budget for housing supplies. It really varies whether or not things like pillows, hot plates, and water boilers are included.
If you're moving into a place with roommates, chances are they'll already have almost every major appliance you need. In that case, you'll probably only need to buy your own bedding, hangers, towels, and other personal items.