I'm not sure of ferret prices, but I think good ones can be had for less than $100.00...
I would recommend getting them while they are very young so that they are more adapt to bond...
Most important tip I could ever offer is: Don't blow in their face!
They don't like that and may end up piercing your nose for you...
All in all, they are great fun loving animals that have an insatiable curiosity streak... I had mine (Kit) for 3 years and loved every moment of it... My cat and it finally came to an understanding which made it much more enjoyable whereas before, all they would try to do was creatively eat each other...
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Terra
--To smell or not to smell, will be the final question--
FutureQuest