99, in the Janesville area, Bob Kimball Enterprises has storage that would be big enough for your unit. They are pricey, though, at around $150 per month, with a 5 or 10% (sorry, can't remember which) discount with a years commitment.
The units are located on Delavan Drive near the GM Plant, and are relatively new.
I'm in northern Illinois but the same solution may apply. I store my 30 in a local county fairgrounds building. Boats and RV's all go into storage on the first Saturday in November and come out the first Saturday in April. The prices are very reasonable ($7.50 per foot).
Check with some local farmers. I rent a spot in a machine shed on a farm in Green County. Granted it is 50 miles from home and has a gravel floor, but it is under a roof and I can work on it or get it out with out notice (just have to move the boat out of the way first). Also some county fairgrounds have storage, I know I used to see a lot of RV's at the old Jefferson County Fairgrounds. My spot is not prime but the rent is only $100/year ( they also have acess to my generators).
I see you listed Darien as Home. If you know anyone at the cannery they may have a line on some old dairy farms that converted to crop farms and have barns. There are a lot of farms like that between Darien and Janesville.
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