Always perform a "wet funds" closing.

Most investors rely on hard money lenders to secure non-homestead/investment properties. 

The best way to acquire this MHP is probably via purchasing the non-performing note and either executing the foreclosure or pursuing a quitclaim deed.

My plan is to secure a 3 or 4br on an FHA loan as an owner occupied.

Events like that rock your sense of security even though they have a very low likelihood of reoccurring.You might want to ask the police their thoughts on your best course of action and/or responsibility.We've had garbage like that while occupied by the loser tenant, but not after. 

If you want more you can hire an agent to purchase the house and get contractors to perform the work under your supervision.

I gave them a 1 year lease with no raise to their low rent. ( I know - dumb).now that it’s up I’d like to raise rent And offer them a 2 or 3 year lease so I have security. 

My primary focus is to great passive income and too secure Financial freedom so I can enjoy the time I’m given with family and friends.My main focus is buy and hold rentals (single family, and multi units) but wouldn’t be opposed to a fix and flip or wholesale, I personally think having some of both helps with an exit strategy depending on the market.

I might do it if the agency would be responsible for rent and security deposit/damages.

Personally, I wouldn't own a rental that is negative cash flow, but you need to compare your performance with what a multifamily property can do as well.