So much of this depends on the many, many options for supplies, decorative pieces, everything that goes into building a house. If you have chair rails and crown molding and cool brick on the outside and onyx countertops and everything else, the price per square foot is going to be higher than it would be for one built using more inexpensive materials and simpler design. You might want to check with your local Habitat for Humanity and ask them about how much their houses cost. I rather think they’d be willing to help you figure it out.