The problem that most folks run into when it to determining a rate to charge for contracted work is they typically charge to little and end up in the hole at the end of the day. Today is your lucky day, as I am not a contractor in your general area for the service that you will provide, I will help you out.
Send me a PM and I will get you started.
Do not worry about the cost of insurance taking your first years pay, that is typical of companies that have not applied the proper rates for there work and at the end of the year cannot figure out why they lost their business. Do not charge per hour what you need to make, you will be in a hole before you even set foot on a job, professional contractors do not operate this way.
Those are the guys that are always taking about making tons of money week to week and then their BMW's and boats get repoed when the phone stops ringing.