Kids? Fine.
If hifi kit survives kids’ earliest years, it’s solid. If kit survives kids’ teenage music-discovery years, it’ll beat kryptonite.
Dogs? Fine.
Dogs might shed, they might drool, but they also guard the home against burglars breaking in to steal a listening session.
Birds? Fine.
Bird dust will coat the kit and protect it from ill effects of tar etc. should there have been any smoking on the premises.
Cats? Fine.
Better that cats perch upon / sleep atop the kit than had the birds.
May prevent coin deposits in cooling vents; caution top-firing woofers.
Cat dander - see Birds.
Reptiles? Fine.
If you contract Salmonella from the kit, you know the previous owner didn’t douse said kit with sanitizer spray, and so perhaps also avoided Febreze.
Fish? Fine.
Aquarium-borne humidity simulates a subtropical / coastal environment and certifies the kit’s gold plating is authentic.
Ferrets? NO.
Smoking? Fine.
Tar will seal up the bird dust / cat dander coating and thus protect circuits from aquarium-borne humidity shorts, especially kit with cheap / worn plating.
#1 on my No-No’s Top 10 List?
“Foam party-free.” Not to be confused with “Foam Party - Free!”