I once heard that nowhere on Earth you're ever more than 6 meters away from a rat. I don't think that's true, but it's probably still a bad idea to blindly assume that there's no vermin anywhere. You keep vermin away by not feeding them.
I see that as realistic, if we are talking 2D spaces. In urban environments, they live in sewers, and you have sewers under every building. In the countryside, they obviously live everywhere.
I can see that 6-metres rule broken only if going 3D, i.e. in multi-storey buildings with spotless maintenance of any nook and cranny, living on the third or fourth floor, you might be a bit further away than that.