This answer has been posted to a similar question. Hope it helps you. A per square foot price is not as accurate as you would hope, but it does give you a general price range. Many factors must be taken into account. Foundation and lot conditions, the quality of materials used for it's finish. Speaking to a contractor in your area is certainly the unavoidable starting point. You can also contact a building designer/architect in your area. They can provide you with the plans that will both help you bid the project, but prepare the project for permitting. Permitting will be required unless your area is very rural and the county does not require this step. Contact AIBD.org for a list of qualified building designers in your area. They can also provide you with a list of quality builders to bid your project. Good luck.
I specialize in rehab and construction-perm financing. If you need a good builder/general to contact, I could set you up with one. I'm local (I live in Naperville) and my contractor's are local as well.