The tenant apparently had some family issues and made the living room into a separate bedroom. He did this on his own dime, of course.
What steps do I need to take here?
Hi Sam-
In my lease, I have a section that states "no improvements/modifications to the unit without landlords permission." if you have the same general section in your lease, I would send a compliance letter to the tenant and let him aware he needs to take down the makeshift room or consequence xyz will happen as this could lead into future issues/modifications.
The tenant apparently had some family issues and made the living room into a separate bedroom. He did this on his own dime, of course.
What steps do I need to take here?
I'm with Garrett. My lease says they are not allowed to make alterations without my prior written approval.
If this is a temporary wall that isn't attached to anything, then there's nothing you can do about it because it's no different than a piece of furniture. If it's actually hard-mounted to the walls, floor, and ceiling, then you could demand they return it to the original condition or terminate their lease.