There is no such thing as a "Tea Cup Yorkie" anyone telling you that they sell teacups doesn't know what they are doing and are trying to profit of you. Yorkies should be bred to the standard
About Yorkies
I can not emphasize this enough if you are looking for a puppy you should be much more concerned about the health of the puppy, the parents, what health tests have been done etc. than what size your puppy will be.