You also need to develop a mind set about protecting the ferrets from harm. Although they act pretty tough, because of their small size, they are rather fragile. To ferretproof, you need to crawl around your house on your hands and knees, and look for any small hole bigger than 1x1 inches, and plug it or block it off. This includes ventilation ducts that might be able to be pulled off, cupboards that have holes inside, appliances such as refrigerators, stoves, dishwashers, and washing machines. Never assume that a ferret will not get into a certain room or area.
Furniture needs to be carefully checked over.
Recliners and sofa beds can be death traps for ferrets. They will crawl under and get up in the gears, and when someone sits down or operates the gears, the ferret can come to an unpleasant end. Even though you may think you know where the ferret is, never assume. Many ferrets have died that way. Regular couches also need to be ferretproofed.