You live in Tampa and never heard of a house or Double Wide or Manufactured Home on a single lot with a Well and Septic Tank?

Rent the house-$600/mo, rent the pole barn for storage-perhaps 10 boats at $300 for the season, rent  the land-$2250 for a year, put up a billboard as the property is next to a county highway with good traffic.  

She knows when a kitchen is missing something important, like plenty of counter space and storage.

Some ideas I have based on the location and traffic count include an RV Park or Self Storage.

why are there so many storage facilities for sale

These rules shall apply to, but are not limited to, noise, odors, disposal of trash, pets, parking, use of common areas, and storage of toys, bicycles, tools, and other personal items (including signs and laundry), which must be kept inside and out of view.

As far as damage.... most of them have worked out well....The first thing that comes to my mind is if the house has a septic system.... if you put too much use on that, you should make a required charge of a tank pump.Next:  A win win should be doable if they are decent people.  

Need to define asset type within commercial ( retail,industrial, multifamily, office, warehouse, self storage, etc.)Next define the deal size 1 million,5 million,10 million etc.Without this you are just throwing mud against the wall and seeing what sticks. 

Does anyone have a rock solid Storage Unit Lease that I could edit and use?

Of my 2 rentals in Dundalk, one has a cellar area for storage and utilities and one doesn't have a basement (mono slab) and both were a challenge to rent -- it took months to get a good tenant.