As already mentioned, there is really no way to provide an estimate by square footage without knowing the specifics of the project. Everything from windows and doors to siding are going to impact the costs.
The amount of work required to pour the foundation could be very simple, or need major excavating.
I agree with getting several bids; however, the lowest bid is by no means the sole criteria for hiring a contractor. How are you financing your intended project? Have you thought about using an FHA 203K loan? Without a doubt, it is the least expensive way to finance construction costs. I would be happy to clarify the product and process for you, if you have any interest. Best of luck to you!