Hi: I don't know much on how this site works, but I'm giving it a try

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I have a question for Yorkie owners. I have 3 Yorkie's

(ages 14, 3, & 2). two are spayed/neutered, one is not, (she has high liver and can not be put under anesthesia).
Anyways my question is. I want to start breeding Yorkie's.
I want to know how can I find a male and female dog that are in good health, have good blood lines and registration, that are clean in genetic conditions, and that are not more then 4 1/2 lb each?
Is it better to get adults or puppies? Is it better to get only a female and find a stud? I know the female has to be 2 years and needs to go to the vet to do test, but what age does the male need to be, to be able to breed?
As you see I have lots of questions, and I want to be well informed of every thing before I get the potential parent Yorkie's

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Please help me find answers to my questions. Thank you all so much in advance.
Also if it helps I am studding to be a vet tech and pet groomer, I also do volunteer work at a vets office. Thanks again.