Hey Brettski,
I'd take a different tack.
After reading this whole thread it looks like you'll be ending up with a full blown residence with electricity, water, heat,septic, full footers, decent windows, etc. Depending on your tastes I would think $60-$100 per sq. ft. That's a big buck for what will turn into an outbuilding in 10 years.
If I were in your position I would choose a plan for the permanent residence and then start building piecemeal. I'd start with the garage (2-3 car), put a second floor on it and use inexpensive 2X full span trusses for the roof. You could slice and dice the room layout or leave a large open area without regard for bearing walls.
With a little preplanning you could locate plumbing, electricals, foudations, doors, etc. to be integrated into the final design. The temporary living area could either be incorporated into the final design or demoed. That way you'd get double duty out of a portion of your work and material.
Just some food for thought. I'm just starting to drywall my new place after 3 years of evening and weekend work and I know I wouldn't want to start from scratch again in another seven years.
