Also, it has three flights of stairs so its not a good rental unit for seniors. 

I like what you did with the stairs.

A first important part is knowing your type of foundation, and what if any reinforcing will need to be done for the area that will be exposed from the stairs running along it.

In addition to that, I added mini splits in the up stairs and addict  rooms to make heating and cooling way more efficient as well as put up a wall and door for an office on the second floor.

Me and my wife's first MFR we purchased (10% down conventional) we moved into lower unit, gutted up stairs and renovated.  

Looks like there is a water runoff problem which is causing the ground and cement to crumble away.

I actually spoke with an investor yesterday that is planning to spend the time and money on updating a back cement patio on a 700/month rental haha!

Alternatively, you could offer to pay for an easement for the stair case from the neighbor.

My good tenants were upset (understandably) about all the noise (running up and down the stairs) and traffic.

Hey, I am looking at a multifamily property and had a question about the significance of the damage to the cement slab on the back side of the property.