Prebuilt portable garage shed?

I am looking at buying a prebuilt portable garage shed that would be 12x28. I would be buying it store my duster in it over the winter along with some other stuff. Does anyone here use one for car storage and if so how is the wood floor holding up? The specs on the floor would be 2x6 floor joists 12 inch on center with 3/4 subfloor for the flooring.

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