I qualified as a pest control agent in California years ago. A point in fact, I maxed out the 100 question test. A: You need to find why the rats like to live in your area and eliminate the reason(s). Generally they have found food and shelter. I have even found rats eating human feces that had a high level of undigested corn meal in it. B: Block their access to the property/home. Fine steel wool or "Brillo" pads shoved in the holes if you can't afford repair work. C: Clean up the grounds around any homes or structures. Thick ground cover against the walls is a no no. D: Yes, properly used, poisoned baits can work just fine. E: Call your local Vector Control agent, usually a County agency, and ask for help.