tgello,
I'm late to the post here, having read the other replies, just one thing to offer if you are considering stick built as well, as I found the pricing to be very close to pole barns here.
In monolithic slab construction in NH the codes require a "haunch" which is essentially a 18" deep x 24" wide perimeter with #4 rebar in an upside down J tied every 24" into 4" square 8 gauge wire mesh in the center of the pad.
This is after site prep of course with bank run gravel (1/2" stone with sandy mix) compacted all around 3-5" deep.
In addition, 6 mil poly is recommended to prevent moisture penetration and sweating in the summer, and if heating the bldg 1" or so insulation is optional on the sides and floor before rebar setup.
The footers/framing are 2x12's around the exterior set to the finished height you want (typically 4-6" above final grade)
The pour is 3000# concrete mix, and for a 24x36 building was around 20 yards - $2600 complete with footer framing, rebar, mesh and finish, including the cutting every 12' for expansion/crack prevention. We then framed on top of this with a base of 2 PT 2x6 then std frame up from there.
So far two bldgs done this way (26x42' Garage/Office and 24x36 Barn) are holding up well.
Carl
This is