Forgot. It is his right to show the unit to a potential new renter. I don't know about the rats. Think of Walter Disney. He made a big business out of the rodents in his apartment when he was a nameless painter, …
Before you move to the house or apartment, you should inspect it and write everything about the window, door, kitchen, and floor conditions on paper. For instance, the window screen is broken; the range top is dirty; there are 10 holes on the wall... and so on. Keep one copy yourself and give the landlord another copy. This is the best way to protect yourself from the very beginning.