Hi and welcome to YT

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First and foremost - one of THE most relevant RED FLAGS when buying a quality yorkie is to 1000% avoid any/all breeders who claim they sell/have/breed "teacups" - there is NO such thing as a yorkie teacup. Unscrupulous breeders use the word "teacup" as a marketing / psychological tool to make you think there is a specialty and to drive up their prices that YOU pay.
ALL yorkies are considered standard yorkies at 7lbs and under. There is NO teacup category - never has been, never will be. That word is considered a huge no-no by ethical breeders.
Find an ethical person / breeder to deal with so that you end up with a healthy, well-bred puppy.