Since my poor old house is non-repairable, we're going to have to build new....looking at a Morton Building shell that we would finish interior. SO how do we decide on a foundation? We want as inexpensive as possible, but still good as far as energy efficient and ease of future repairs, etc. The salesman is pushing for a concrete slab, but I've never lived on one and don't know the pros and cons. We are in central Illinois. Any advice or opinions would be MOST appreciated. Thanks!