I understand size is a concern for you, being able to care for them. In that case, you would be better off looking for a Yorkie breeder who has young dogs who are fully grown. Breeders can make a good guestimate on adult size of their pups, but there is no guarantee. My boys are full brothers, different litters, and they grew larger than their littermates. My boys are above the Yorkie 7 pound standard. We knew Max would be a little larger, but Teddy was a bit of a surprise since he was barely 6 pounds at 8 months of age. He is now 9.5 pounds, although a skinny boy.
Show breeders often hold back pups and then later release them to pet homes.