Very rarely, those cases happen due to some fat tails event-- recession, war, pandemic, etc.

If you have the storage room, having one of these might be handy for future SC summers, as I'm sure this will happen again at some point.

Audit expenses and cut the fat.

Has anyone ever used conex / shipping containers as mini storage?

If your properties under management are generating steady income for you close to or even exceeding your initial expectation, yet you scan the work orders and find more fat that can be trimmed which would yield even more profit.

Now today on the 20th at 130pm with a close tike of 3 pm, the underwriter decides that they don't like that because I'm so young and so fat have only been an authorized user on a credit card (having been renting and paying for utilities for a year though) and haven't been making the payments, that now I would need to have a cosigner (which doesn't really work since everyone I know have too many write offs) so now I'm in limbo while I wait to see if there's any other solutions.

There are 51 storage units on the same property.

I could also leave a unit within the multifamily property vacant when I am abroad to use for storage if needed, to better help solidify the "primary residence" requirement.This is a pretty specific question, so I haven't been able to find any previous posts on it or any helpful literature online.

The last thing I would want is to have a property break even with no fat to skim as a contingency. 

Your post, @Steven Westlake, reminds me of others here asking about car washes and self-storage facilities.