We have electric mouse traps. The mouse gets electrocuted and you can dump it out of the trap without touching it. We put ours in the woods for the foxes, but you can dump them into a bag. If you poison the mouse and it leaves the house, you'll probably poison whatever eats it. And they might die in your walls. They dry up pretty quickly, but do smell bad for a week or so.

Cats are very effective against mice. Often the smell is a deterrant, so if you don't have cats, but have a friend with a cat, used kitty litter under the crawls space might work. Mice have better noses, so they'll smell what you can't.

You want to know what kind of mice you have --- house mice or wild mice.

There are granuals you can buy at the farm and home stores, and it gets sprinkled all over under the house, to keep mice from wanting to come there. Its the same thing, that people use when they rent storage buildings when they need to store belongings, for some reason or another. It deters the mice from trying to get under the house.

Look up "bucket trap" for mice. Very easy to make one yourself with a 5 gallon bucket, coat hanger and a soda can. You will catch mice.

Please don't use poison. Other animals eat the poisoned mice, and get poisoned too.

The best solution is to keep them out. Mice will chew through wood and plastic to get to warmth and food (ask me how I know this LOL).

Metal mesh made for installing tile is a good barrier. It is like hardware cloth but less expensive. If you or someone you can hire can get into the crawl space, buy enough rolls of the mesh to staple over the insulation and the cracks between the joists and the "ceiling" of the crawl space. It can be cut to fit. (ETA: cut with tin snips) Particular attention to the corners where joists and side walls meet. Mice can get through a surprisingly small opening.

There is also spray foam pest block, which I would use also to seal cracks and gaps. That will block ants and other insects from entering as well as a little extra against the mice.

They will sometimes nest in insulation, or have urinated/defecated in it - possibly you should replace any that is damaged but inspect it before deciding to replace it all. Spray foam insulation might be a good choice if you decide to. That will also act as a barrier.

There is a bait called Mouse-X (or Rat-X ) that is none poisonous, so it is safe for mouse predators, but it is like an overdose of fiber that the mouse can't survive. You could use that to rid the interior of any mice while you get the house sealed up.

I've heard that organic bait makes them so fat they can no longer enter holes where they can hide.

There’s no one best way to keep mice from entering your house or ridding your home of them once they’ve moved in. It’s a multi pronged approach that you constantly and consistently work at .

Echo the comment on the battery powered trap. Electrocutes them, and then they look like they are sleeping. Works great. OWLTRA

A garter snake