Also, even if I let them stay and they began to pay rent--no one should inhabit the property in its current condition (I don't want to be a slum lord or do anything illegal by allowing this person to stay in the property). 

So if you are a civilian it's  N/A.

My main concern is in regards to my 2 year work historyI’ve been a union carpenter since Jan 2018I’ve been in the military since June 2017I been constantly going back and forth between civilian and military work but have been constantly working.

Usually if you have to occupy the property, during escrow you should have the seller/listing agent inform the tenants of the unit you will be inhabiting that they will have to move out when their lease is over.

In regards to breaking the lease without penalty, I was aware of that, but I don't think I'm too worried about the vacancy because how long can I expect a civilian to stay renting in one place?

The burn pile should be a thousand feet from an inhabited property.If you rent the property, you are guaranteed to get complaints and get reported to the state for illegal burning. https://www.epa.ohio.gov/porta...

I'm essentially a civilian in uniform, we deploy about once every ten years.

So now the house is not inhabitable because there is no sewer.

I don't disagree with your definition but like you said that is a bit narrower than the actual definition:Gentrification: "the process whereby the character of a poor urban area is changed by wealthier people moving in, improving housing, and attracting new businesses, typically displacing current inhabitants in the process."

Unfortunately, two weeks before closing, one of the units had a small fire due to electrical issue that render that unit inhabitable.