Adding a few storage units to small multifamily

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In escrow on my first MF. There is room next to it for some storage units (for tenants). I can easily fit a 500 sq ft building in the space. I am considering building this as a large shed with separate 10x10 spaces. If I build a 5 space "shed" I could use one for my stuff too. I'll be living in it for a year. I could also store landlording tools etc. 

I found something similar online. Any other options? I know there are prefab storage units too for like 12K? I could have a wood one built for much cheaper 

Trying to think how to test this too? 

Wood shed example