I don't know exactly what you will need because everyone's situation is different.
I spend money on fuel, service, health insurance, liability insurance, food, postage, internet to fax bills etc., phone, collision etc, insurance., and probably more I am not remembering at the moment.
One thing I think I can safely say. Whatever you think you need money wise, you probably need more than that.
I would not try to do this on a shoestring, as there are always unforseen costs.