Is the unit being used for illegal purposes, are they destroying the place? 

Assuming that the boards underneath aren't destroyed you are probably looking at $20,000-$25,000 just for that. 

Although thats may be an opportunity, many wont know how to get it due to inexperience

My backbone has been retail Commercial and I've been around the 15-18 % CoC on those deals so Maybe my projections for multi-family may be a bit off but they are attainable , not 20% but I've talked to a few investors where they are getting 12 % + but i know they wont spill the beans on where they get the deals , we are in a smaller market ( 120k population ) I want to focus on Multi-family and really get educated as best as possible on it , I dont want to touch any other asset class .

House value is about $150000 and mortgage is for $140000, doubt a investor would take it off my hands for $140000 but that’s why I’m asking.I had a leak detection company into detect if it was aunder the slab pipe leaking but they did not find anything, I do not know if it’s flashing around the chimney or the fact that there are no gutters causing water to come in behind siding or flood over the foundation.The dishwasher was leaking a ton of water so it could just be that not sure tho.My question is, is there a way to walk away from the house without having to ruin my credit I have an excellent credit score, I don’t know if an investor will be able to take it off my hands or is there a way to give it back to the mortgage company without destroying credit?

However, if a landlord has a tenant who can't (or wont') pay rent they can ask for rent and hope for cooperation but can do nothing beyond that to improve their situation.

or sense those are two units I am operating a MFH in a SFH which my zoning peeps wont like too much.

If you refi, you would be paying interest regardless of you are able to use the money or not.I prefer LOC since we wont have to pay interest while we dont use it.

(IT WONT)No other tenant/buyer will want to purchase the house at a price close enough to what I even agreed with seller. 

But what will happen for sure is that mortgage and eviction protections will lift and people who have destroyed their savings will be hungry for cash.