Would you consider labor only arrangement and source lumber package yourself? This should save you money since you won't be paying mark-up on materials. This also gives you more control and clarity over quality and exact type of materials used. I am in Chicagoland but currently building in SW...
Sorry for reviving this thread. Yesterday, we poured a 4' ICF stem wall foundation for slab on grade house in SW MI. Soil is sandy but water table is also high. I intentionally set footings slightly higher than current water table but not sure how high the water table might be in the spring...