I rented a storage condo in the greater Phoenix area when real estate was somewhat depressed, about 15 years ago.
Loved the condo. Huge opening, huge/ tall overhead doors. Could put anything I wanted into the condo.
The issues, IIRC no power was allowed in the condo. Might have to assume in the Midwest, heat might be an issues. My observations was 80 percent of the owners rarely went to the condo. The other 20 percent were always there, often/ regularly blocking other owners doors, etc. This small condo storage development had a full time manager- so I can imagine monthly assessment fees were high.
Think they are a decent idea, but like any condo- it comes down to your neighbors/ other owners. You don't mention where in the Midwest you are. Midwest might be harder to resell when compared to the south/ southwest, etc. Picking the right unit in a development is also part of the decision making process. Is your unit away from high traffic areas (like the entrance exit)? Is the condo at a turn making it hard to load/ unload without blocking someone else?
Supplementally- I suspect most rules prevent a business from running out of a storage condo. I found were I was guys weren't running a business out of their condo, but they were indirectly operating a business out of there condo. Is a contractor owning a unit, leaving nails and stuff regularly on the condo driveway? Does the contractor load/ unload heavy equipment on the driveway that wasn't designed to handle the weight? All issues to have awareness of as part of the decision making process.