Ferrets just stink, period. mother in law loves them and has had up to 6 at a time. I hate them. Told husband, when we got the house, one ferret or one dog. mother in law said take the dog. Thank goodness.
They're sweet though - when they're not biting!
Possum has a recurring NASTY urinary infection - about every 2 years. Urine smells sweet and mildewy. Something else to keep in mind...