I paid something like that at our previous house. The guy spent hours looking around the outside, caulking up cracks, etc. Then he put the kind of poison bait stations they use outside of restaurants in strategic locations outside the house. It seemed to work.
This house has mouse issues, to be expected because we're in the country and everyone does to a degree. I had the exterminator put out the small bait stations as part of the regular service. They're working, but the mice keep kicking the bucket in the house. And I never find them until they're REALLY dead. Blech!
and "Bonus Mom" to: