Getting into NYC is next to impossible unless you know someone in a high place. Deals are cut on the inside in the NYC. The first thing you will have to do is contact the NY State Insurance Fund for workman's comp http://ww3.nysif.com/Workers_Compensation.aspx
Next contact http://www.nso.com
for your professional liability insurance. You will not be able to get general liability through NSO. You will have to go to a commercial agency. Most will not cover nurse staffing and when you do find one it will be expensive. After you do those things then you can go after contracts. Let me know if I can help.