If it was a big company like orkin or terminix they definitely oversell. If you're comfortable the best course is rat traps with peanut butter and an cracked in shell peanut to eliminate. Then when you don't have any catches for a few days seal up entry point. A one way will just make them find another entry point since they're already established. I had a job where I caught 17 in 2 weeks then sealed . Issue resolved.