Security deposits do not belong to the owner until/unless the tenant leaves and there is damage beyond ordinary wear and tear. 

What @Thomas S. said, plus the fact that if you let them use security for last months, you have nothing for property damage.

It has caused prices to increase but, nothing astronomical. 

The other neighbors don't intentionally cause me trouble, so I don't feel the need for more than the existing chain-link fencing on those sides.

We're leaning towards a property manager cause we'll be out of state, are not terribly handy, and both will be busy with our careers. 4) What's the best way to go about getting it rented out?

I think the back two units had fire damage.

I do m2m cause it’s easier.

It would be a win win cause we would be staying rent free and he would be saving on utilities and upkeep.

Then you'd have to make sure there is no mold or other water damage that was caused by the leak. 

If the person is inclined to help then great , that Is a worthwhIle cause but don’t mix business with it .