As the house is for sale eh?
Hey d00d, it's not a bug, it's a feeeature!
"Quaint haunted house for sale. Has ghosts that come out and bump around at night..."
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A few years ago I had *something* in the crawlspace. Whatever it was, sounded to be about the size of a cat and made its nest directly under the bath tub. Occasionally the noise made me think it had managed to get inside. There was no way I was going down under there, and it was only intermittent, and eventually it went away. Personally I *really really dislike* crawl spaces, they are an idiotic idea, they are usually hazardous as hell, and they are a classic example of sh---y California construction. Give me a poured basement any day. By the end of next year....
We used to have a regular group of racoons that would come down the street the night before refuse collection every week and get into everyone's bins and make a mess all over the street. They seemed to be highly organized, and have moved away since then.
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Racoons are only mildly nasty compared to 'possums. Squirrels are cute as hell, I think of them as almost like pets or something.
However, all of these can carry fleas that can carry plague. After you chase the critters out of the attic, it might be worth while spraying for fleas.