My friends once had a dog, a cat, and a bunny. And despite trying to clean up, spending an entire day there actually caused me to suffer pretty severe allergic reactions.

The bunny passed away so it's slightly better (esp if I wash my hands every hour) when I visit.

Bam.

Personally I've never had more than three pets in the same house, and only temporarily. At home it's usually just one pet at a time. We don't have time to take care of farms.