Sounds like a repair, not an improvement as it does not prolong the life of the property, enhance its value, or adapts its use. 

I don't want to run risk of having no tenants for a prolonged period and being on the hook for the entire mortgage. 

Mistake #2: didn't research enough on how bank internal efficiencies can prolong short sales.- Very short closing period.

to prolong the life of the unit and reduce chances of problems?

This means there is a drag on return via decline on property values and to some extent additional capitalization of the real property asset and the pro-long hold time.  

You can always go and hope they don't make you but they usually will in which case they will give you an extension which will of course prolong the eviction.  

Flipping/wholesaling also have high returns but are not considered passive at all.I own a couple of properties in 29 Palms that were purchased a couple years back and the returns have been good, but they have had some headaches with turnover and prolonged vacancy. 

My passion is modifying residential places for senior, so they can prolong their life in their own environment, and eventually develop my own senior residential complex.

People that are squatters and know how to find the name of the previous owner to create a false lease usually know the system and know what to do to prolong their stay - like responding on the last day.

That prolongs the closing process 3 additional weeks now i'm really skeptical about the seller now Weeks later with daily communication to insure the progress is moving forward.