Most good breeders will offer a health guarantee with their puppies. Be sure to inquire about this when you're choosing your puppy.
It is important that you feel the breeder is diligent and watchful in their breeding program, and that they avoid breeding to any Norwich that have any health problems in their background.
Are the breeders doing heatlh testing?
What are they testing for?
Ask for references supplied by the breeder of other people that they've sold puppies too.
Ask many questions pertaining to health and temperament of the parents and relatives before you buy.
Try to see the parents of the dogs that you are purchasing, if possible.
You can be sure that a good breeder will also be asking you a lot of questions and expecting references from you as well.
They will likely be asking you:
It costs money to breed good dogs, so don't buy the cheapest Norwich you can find. You usually get what you pay for. Dogs are no exception to this rule.