$500 to $1000 in rent, plus equivalent amount food and entertainment for a non-stressful lifestyle. You can pare down costs to perhaps $800/month by getting a room in a shared apartment and eating inexpensively. Add on $2500 annual expenses for visa, entry-exit expenses, etc.
Hiring programmers costs between $500 and $1500 per month depending on skills and experience. Without a legitimate Chinese business it can be hard to attract talent since you will not be able to pay social benefits, etc. Starting a legitimate business costs upwards of $30,000 in a one-time incorporation expense and pushes hiring costs to about $1500 per month per staffer.