During an inspection by the city, it was noted that the system lacks a backflow prevention device, which is not up to city code.3.

@Johann Jells Thabks again, it turns out it was the heat exchanger between the boiler and the storage tank.

The stats are: -5 stories totaling 20,000 square feet above ground, plus a full basement which is partial commercial space and partial tenant storage/utilities-First floor commercial space is around 2300 square feet with an additional 1500 in the basement, 12' ceilings in the first floor-14 residential units above, most have private balconies or decks, elevator, bike storage, mail room.

Around 25 years ago, I knew someone who owned a building (shed), a few mini storage units on a lot in a town.

My thought would be that you could probably buy a smaller mini or maxi storage facility and self-manage it. 

., My original quote for this thread was up to $600k, that was my highest bid when I was trying to have a 4 family built in the style of All Brick with each unit running 1000 sqft [became to small for a 3x2 for what I wanted], for 4000sqft total size on a full basement used for garage space and storage.

This is a triplex with an option to also rent out the garage for storage.

The outbuildings will not be used for vehicle storage or any storage for that matter until I replace the roofs.

In most states, an undisclosed audio or video device placed in the interior (non-common) of a private residence would be illegal and could also result in a civil lawsuit against the landlord. 

Why not look into buying a storage or some mini-mall.