I think this is perhaps the most important requirement to have a healthy and happy pet. As mentioned above, Ferrets need daily interaction and playtime. It's not fair to leave them caged for an entire day. They can become overzealous in their play and sometimes nip too hard. With a little patience and training this problem can be alleviated.
Ferrets require annual vet visits.
Ferrets and all animals should be supervised when around young children. Do not allow your ferret to chew on foam toys or foam cushions from furniture. Intestinal blockage is a serious condition that can kill a ferret within a day or two. Before you buy a ferret or any pet, make sure you consider the commitment that you have to make. Buy a book, talk to a vet and do research on the animal.