I have been managing his portfolio since mid-2017 and it was an ideal situation for me to be in.

This is because you have to furnish and pay utilities that you wouldn't in a standard renting situation.

I could use some advice  and or recommendations on what to do in a situation.

Happy to share more details for those interested in my situation or want to charitably help me make some critical decisions in the next couple days.Here is Brian's article I'm referring to: https://www.biggerpockets.com/renewsblog/2013/01/2...

The question is, how will your property be financially situated, absent STR income, if you switch to LTR, can it cover the debt?

In your situation I see only one possible option.

On further looking into the details, I found out that he has also not paid any association fees since last few months and now this months water bill is due as well.What should I do at this time to take control this situation to get worse and reduce my loss ?

There was a story on here last year where a tenant scratched another tenant's car - in that situation the LL who hired the shoveler is likely liable. 

Here's what I would suggest in these situations: go find/network with various reputable GCs and ask them to provide a copy of their contract.

It's a little complex but can be very useful in the right situation.