Every breeder has a differant contract, and it is EXTREAMLY IMPORTANT for you to read over your contract and understand all of it, before ever receiving your little one.
Sometimes, a contract will state genetic disorders covered for a year or two but NOT cover any joint/knee problems or vet bills that go with it.
These tiny breeds are very prone to joint/knee issues and it can be either hereditary or injury...
Also, in case of a death, make sure that an autopsy is done at a independant lab, neither the breeders or the owners vet, this is crucial!!!!
I cannot tell you how much I have learned over this past year of having two Yorkie's, one passing away and having to use "my contract guarantee" and one still living but could have used "the guarantee" if I pursued the issue. Sadly to say, this would have meant returning Schatzie to the breeder for a replacement pup. Well, this turned out to be more of a "personal" issue on my part and "I" chose to keep Schatzie and not return her.
I hope this helps...