I live in a older double wide, '75 (tin shack in the woods)..
As these units evolved over time the method of support and anchoring has also changed.. Also local codes have changed.
My house being 'pre HUD' is allowed to be set on cinder blocks without a footing or 'ribbon'. I moved mine 6 years ago and because of it's age and (pre-HUD) I was allowed to set it up by the old standards..
However, I was involved with setting up a modern double wide a couple years ago..
What you discribe as 'sidewalk' is called 'ribbons'. These are 4 ft wide stips of concrete, two per house section, for the entire length of the section. The spacing of these ribbons will be dictated by the "builders manual". This comes with the house and is what the inspector uses to verify that the home installer has done everything correctly.
Due to the 'deep freezes' in Iowa you may still have to go deeper with these ribbons to get below the frost line.. Better check with the local building inspector.. Even if you are out in the country, the county will still have some say about how you do this.
For anchoring, there are pieces of PVC pipe going through these ribbons and a tie down stap is passed through these.
It is possible for you to grade your site and pour your own ribbons, as long as they meet the requirements of the builder and the local code.
There is another consideration you should know about.. If you set you mobile on a basement or a foundation you 'may' qualify for a standard home mortgage. No matter what the mobile home builders/sales people want to call them (sectional or double wide), the banks still call them mobiles and won't normally give you a 30 year mortgage. The mobile dealer will argue that he can get you a mortgage but it will not be a 'home mortgage' and you will pay thousands more in interest over the life of the mortgage.. My point, recently I have heard that some lending institutions will go with a home mortgage if it is on a foundation.. Home owners insurance will also depend on whether you are on a foundation..
For your area, due to the freezing ground/deep frost line, I would recommend you at least have footing poured, if fact that my be your only choice, depending on the local codes.
Your manufactured home dealer can give you some recommendations on what you can or can't do, but 'keep them at arms length'.. They are out to sell you a mobile home (and call it a sectional, modular,etc) and making a big profit off you and most likely a kick back off the guy who sets up the house.. (The deal farms out that work)
There is another consideration in doing the ribbons or foundation yourself.. The dealer or mfg may blame any problems or defects on your work.. But in my opinion, if your ribbons meet the requirements of the manual and code then let them due the final set up and leveling.
You can also do your own utility/plumbing hook up if allowed by local code.
Hope this helps. I'm not a big fan of mobile, manufactured, double wide or sectional homes.. They are cheaply built because they don't have to meet building codes. The don't retain their resale value.. Never appreciate in value.. And seem to attract tornados and flood waters ;o)
Steve (formerly of Bondurant IA)