Hi!
Your post was from a couple of months back, so I don't know if you've made it to SH yet. If not ...
The average income of a local office worker is less than 2000 RMB a month ... by those standards, you'll be relatively loaded in any case.
More realistically for a Westerner though - Most more established schools such as EF, Wall Street English & Shane English Schools pay from 8000 RMB per month and upwards. I can assure you that there is tons of available teaching work here. If you're not happy with your first job, you can move on quite easily. I've recently changed jobs and am at EF now ... a great company to work for in my experience so far.
I have a 1-bedroom apartment in a very convenient, central part of town, near to the subway & lots of Western type bards and restaurants. That costs 2500 a month. Monthly bills are never more than 500 RMB in total, including ADSL.
Buying food from supermarkets is very cheap & you can live very well without spending too much. The only expensive thing in Shanghai is drinking at Western bars (40 RMB + for a large beer), but most places have Happy Hour with cheap drinks or 'Buy 1 get 1 free'. Check out a chain of bars called 'Windows' when you get here. They are aimed at the younger Chinese crowd and are the regular haunt of English teachers. Windows Scoreboard in Huaihail Road is a great place to meet lots of other teachers, if you're comin here alone.
There are plenty of possibilities for additional part-time and private teaching, which can improve your budget drastically. 150 - 250 RMB an hour is a rough figure depending on the client.
DON'T ACCEPT A FULL-TIME POSITION FOR LESS THAN 8000 RMB A MONTH!!
There are more vacancies than there are teachers, and plenty of very good schools to choose from. I can certainly recommend EF highly (they offer a loan of 8000 RMB upon your arrival to help you get set up with an apartment etc., which is very useful. Check out
EF .com
Hope that helps
Richard