Only six more months to go!  April 15 is just another fine spring day, since the invention of Form 4868.  But to answer your question, I had a client who owned a storage rental (business?  but is that the right word?) many years ago.  Sold it at a profit.  Like many, it had a resident management couple who kept an eye on the place and dealt with new and departing tenants.  They lived in a small apartment on location, which was part of their compensation.  We put it on Schedule E.  It was 100 miles away from where he lived, and he rarely visited.  The place ran itself, with good on-site management.

I compare this to the issue of trailer mobile-home parks, where the question is how much service is provided to tenants.  And then those are also compared to Airbnb's, for no good reason.  

I visited my own self-storage unit Monday, for the first time in months.  I noticed about 20 vehicles parked in the fenced-off area behind the building.  Mostly RVs; an old school bus; some collector cars.  A boat.  Those tenants are just paying to rent a few square yards of pavement.   

Why do you mention depreciation?  Wouldn't it be the same, either way?