Congrats on getting the best pets EVER!!! My opinion (like to get my tuppenceworth in lol) is adult rescue are the best, you get all the back up when you need it and you are giving a 'forever' home to those who need it. I have handled a fair few kits (got the scars) and boy oh boy are they a handful. Ferret proofing!! if they can get their heads into a space the body will surely follow. As far as your cage goes I have no experience of indoor cages, we have ours in a big pen outside with a smaller one for indoors in an emergency. If you can I would advise in getting velcro harnesses as a lot of pet shop ones come with clips which can be uncomfortable and when your guys do what looks like a 'death roll' to get the harness of the clips don't always hold. Have you thought about names???