The traffic near Financial Street is very convenient. You can rent a house along 13 and Line 4, and live for about 3,000.
Your sister is in the fortune building. I suggest you rent along the 10 line and find a place on SouFun. It's easy to find a house.
You are Dong and I am Xi, which is not easy to coordinate. Better find someone who can get on the subway. It's ok to live on Dawang Road in Dongcheng. You can take the 1 line and transfer to Line 2 to Financial Street, which is convenient for friends to go to work.