Effective pest control professional for mice?

Hi all,

I just moved to a small studio in an old building in San Francisco (nob hill). It is a generally clean building indoor but with a nasty basement/trash area (where mice could definitely thrive). After one week I moved in, I saw a mice in my room, and I caught one two weeks later. Somehow, I'm still seeing droppings a week after that. The mice activities are persistent but irregular in my place (some traces every a week/two weeks?) I have been keeping my places very clean and leave no food for the mice, and this should be a systematic issue in the old building. Is there a recommended exterminator that doesn't charge crazy price (my landlord said I could get expert myself but the price must be reasonable)?