I can completely feel your pain!
We just moved back into my childhood home which my mother neglected. She had mice EVERYWHERE. If you do a little research and see how often they can multiply and how soon those babies can multiple you will see that you can easily lose the fight against them.
We tried one company that basically came in and laid traps, sticky paper and yes, poison. That didn't work because they were still coming in.
Terminex came and we were lucky that we had a technician that actually wanted to help us solve the problem. He went around the entire perimter of the house and found the two main entry points. One was in the garage...up in the rafters the dry wall is not tight around the rafters so they squeezed in there, run down the inside of the walls and made themselves comfortable in the insulation in the basement ceiling. We pulled all the insulation in the basement, OMG gross, but it help eliminate a way for them to nest. They were also nesting in her heating vents...UGH!!!!!! So we had those cleaned.
Do you have a basement? If you do make sure you have those areas cleaned up and access points under control.
I still get creeped out and we haven't caught a mouse in over six months (probably just jinxed myself) lol. I bet every piece of dark fuzz you see you think it's a poop! I worked in a newborn nursery at the time and would 'see' their poop in there! Obviously not really, but it makes you crazy!
We could not have contained the problem without the help of professionals. And yes the poison which bothered me bc i was worried they would die in the walls and smell. We haven't smelled anything yet.
Gross gross gross. I just hate mice. And snakes. I have the heebie jeebies right now!!!
Good luck to you!