We are contemplating having a weather tight shell built for us, and we'd finish the balance. Is it realistic to think that rough framing crews base their labor on a "square foot" cost? I can get a framing package cost for materials from a lumber house I deal with.... but I'm trying to estimate labor before I talk with a GC or a framing crew. I realize there are certain variables that may effect labor price and time to build... but a general method for pricing labor would be a help. We are located in the Northeast. Thanks.