I have a slight sloping lot where I am planning to build my house. I am thinking of doing a detatched 2 car garage (approx 24'x24'). There would be a slight build up/fill to the main garage entrance which will be on the upslope side, then there will be a driveway that goes down the slope around the side of the garage to the back, and there will be a lower level of parking directly under the main garage (entrance on the "backside" of the garage as seen from the street/main level). I envision the lower level would be built essentially as a 3 sided basement, and the second level would probably be built on top of that with iron beams and corrugated metal floor with cement poured on top of it. I'm sure it is $$$, but how would it compare to building two separate high quality finished garages? Where is the big cost going to be, that would be different than a normal garage? I'm thinking excavation, there will also be a daylight basement plus 2 story house built next to it, so it will be in addition to work already being done. Also the engineering and flooring for the upper level garage, but I know they do suspended(?) garages (garage over crawl space) around here fairly frequently due to the steep hill sides they are building homes on in the area.