Snap traps impose a liability on the landlord as children and pets can be injured! A better, professional solution would be to use a licensed pest control company. If the landlord chooses to use self help, then the use of enclosed trap boxes to avoid hazards to children and pets should be employed by the landlord.
Paying for a licensed pest control company to take care of the problem would be more cost effective approach in protecting their investment. Surly a landlord would not want the condition to be prolonged by being cheap? Why not have a professional handle it efficiently to protect the landlords investment?