Ferrets are not for everybody. They are high strung and while capable of affection will never get as snuggly as a cat. Odor: ferrets are related to pole cats and have scent glands, which should be removed. Also, they should be neutered/spayed. Females tend to come into heat and STAY in heat, which is bad for them. Male ferrets will be gentler if neutered. When you choose one, go where there are several to pick from. Pick them all up, one by one, and see how they react. If they tend to bite (and ferrets will bite), choose another. Choose the least "bitey" provided it is healthy as well. They should be handled daily, picked up and petted and played with, so they will stay friendly to you. If they are left unattended, they will tend to get wilder. You must have a cage as they can't be left to run free at all times. They can be littered trained, but don't expect perfection. They need "ferret food" or high quality cat food. I was told, by a ferret breeder, to give mine (yes, I have owned ferrets) to give mine MeowMix, which kept them quite healthy.
Ferrets are wonderfully social animals and are very silly and cuddly. However, they do have musk glands that can be removed (just like spaying/neutering your dog), though ferrets do always have a distinct smell. Since they are social animals you would need at least two, and both males and females have distinct personalities. You would also have to get quite a large cage, lots of interesting toys, and be able to give them plenty of time every day to roam around the house.