@Daryl... The way to deal with mice and rats is pull everything out of the cabinets and off the walls. Identify their little rodent highways... these will be along walls and you'll see their droppings and to lesser extent their piss trail. You NEED to bleach the hell out of that trail because it is filled with pheromones that tell the other mice where the food is and how to get back to the nest. Find ANY holes or cracks (they can compress their bodies to fit through a crack the thickness of a coin). With big holes or gaps fill them with fine steel wool and then cover the holes with sheet aluminum then use caulking to seal around the aluminum. The steel wool hurts their teeth and gums as they try to chew through it so it deters them from that route. The aluminum is to prevent any really tenacious ones from busting through. To really do this properly it's best to remove all the baseboards and fill in the gaps behind them with steel wool then expanding foam. Then trim off the excess foam and use silicone to glue them back on then use paintable caulk to seal the top and bottom of the baseboards to the floor and wall. Do all of this inside of your cupboards as well. After all that is done purchase sealable containers for all dried goods or any other food kept in your cupboards. Every so often after the initial rodent proofing pull stuff out of the cupboards and inspect for the pee/poop trails again. If you find anything suspicious find out where they are coming from or at least the path they are taking and go through the above list wherever possible. Also get some snap traps (glue traps are cruel, gross and somewhat ineffective and poison will make them die in your walls where they start to stink and other pests can feed on the corpses... even other mice especially if they are now starving because you are denying them food).
Oh and always keep toasters, ovens, microwaves, etc... clean and free from crumbs and spills. Sweep and mop regularly. If you live in a house go around the house and find any entry points and seal those up with exterior sealing products (ask the dudes at the hardware store).
So yeah... it's a lot of work but they are beatable and your homes value will stay intact. They can screw up wiring and gear and bring in fleas and disease so it's worth it... your house will also stay cleaner over the long run and you'll have the satisfaction of knowing you conquered a small part of nature. Cheers.