Congradultions in finding a breeder. Just do some checking , and make sure the breeder is reputable. Check to see if the breeder has a health gaurentee on her pups, and they are not prone to any genetic defects , Hopefully both the parents will be on site so you can see them too. It will help you knowwhat your baby will look like when older and possibly how big the pup will be full grown. Check to see if the pups are at least 12 weeks old. Reputable breeders always wait until the babies are 12 weeks.
Remember that their is no such thing as a tea cup yorkie , or mirco mini yorkie's . Those would be a couple red flags .
Best of luck in your search for your perfect little yorkie puppy
Welcome to YT as well.