We do not do site preparation but most of our buildings should be placed on number 2 gravel, 4-6 inches thick, level and compacted. The size of the gravel pad should be about a foot larger than the building on all sides. While we don't do this work, we do publish the following business cards of experienced and reliable excavators. They are all very good but are not associated with The Amish Group.
Excavators (Dave Diggs is in the Rochester area primarily)