I do agree with you that the goal should be long-term ownership and cash flow. 

Ballparking the existing P&I around $4k a month (20 year am, 5% rate on 600k - the amortization might be longer but probably on a higher balance) which is well over 50% of gross rents

Ugh, I hate water issues.Anyway, resident understands that the fix isn't immediate and asked if he could get a reduced rent for his subpar living conditions (collecting the water at the two windows, cleaning it up, keeping belonging away from the windows, etc.).

There might be pre-payment penalties, there will be longer and stricter qualifying, there will be lower LTV of the purchase price and no repair money lent. 

This tenet was the only unit we couldn't get access to ( someone changed the locks) my pm went to speak with her the next day to see if she has a key, and some dude that wasn't on the lease ( guessing her boyfriend) answered the door and said they never got a key and they never used the storage unit. so my pm assumed it belonged to the previous tenant. so we had the handy man pop the locks the gain access for the appraiser.

The additional income is for the tenant that would prefer to rent the Garage as well to park in or store their belongings or both.

The issue will be long term maintenance/cap ex.  

Either enclose it or even better move into the basement where it belongs. 

Since those expenses don't really belong to the 6-plex, and we may never act on the property we are viewing, does that mean the expenses are not deductible? 

He has sold off nearly all of his belongings of any value and is at the end of his rope.