I know I'd get the jitters LOLIt could also work out in your favor - If the stuff isn't old or worn that bad, you could offer to buy the furniture off the family at a very good price and then advertise the place as furnished, which could command higher rent.

this will depend on if he is a guest or if he has established residency. if he has furniture there and mail coming in he is usually considered to have established residency and would need to be evicted. if he just stopped by for a few days, he is a guest and should be considered a trespasser. however, in fuzzy situations police can sometimes refuse to help under fear that they are putting themselves into a civil matter (eviction) as opposed to a criminal matter (trespassing).

The tenant in an upstairs unit moved out after one year and left large black stains on the wall where she had furniture or wall hangings. 

The upside is that he will probably offer to buy your furniture and appliances.

I went by the house and the mailbox is completely full but there is still furniture in the house.

This leads to you going around buying things like furniture and decor further putting a strain on your budget. 

Repairs, maintenance inside to furniture windows, door jams, etc that may fall on owner.

Electricity has been off for days, full fridge of food that is rotting, dog poop EVERYWHERE, most of his furniture and garbage is everywhere, baby room still has crib, changing table even a car seat, hell they left their keurig, the only thing we see missing is their tv and clothes--multiple holes in the walls chewed out from the dogs.

Staging doesn't only help people envision their furniture and how their stuff would fit in, but it creates an emotion of warmth and home.

The way you are structuring the deal sounds good to buy the furniture on the side but I would start lower than $115,000 for the condo!