You may also want to consider City/County resources especially if they need licenses/permits to rent/do business in your area. If they do need licenses/permits to rent there may be restriction/obligations that you may use. For instance a complaint may cause an inspection (that may even cost the land owner a fee) and the regulators may be able to force the land owner into repairs/actions. A complaint even if anonymous, unfounded, or something you did may lead to an inspection. You don’t clean your apartment and the living conditions are filthy the inspector may make the landlord do it.

Where I live the city inspects apartments and the owner is required to make any changes the inspector orders based on codes (and the inspectors perspective of those codes/situation) and can be as minor as forcing them to put screens on a window that has never been, nor ever will be opened, to maintaining fire extinguisher with a current yearly inspection stamp. Failure to comply means they can not get a permit or their current one is revoked, no permit no renters.

Of course there is always fire. (Just kidding, I don’t want the families of your victims suing me).

But whatever you do I would also follow Longshanks advice.