I have a 30 x40. Three 10 x 9 doors. A side small door, four 3x4 windows, two 3x3 windows. It has a loft 7x12x40.
Did most of the work myself. My yard was clay, So I basically put a full foundation (82" wall, 10" footing) and filled it in to pour floor. I have about $16000 in the floor/...