Good for you for seeing the red flags from this breeder. A reputable breeder does not sell Yorkie puppies before 12 weeks, so this is not a reputable breeder.
Check the breeder list from the Yorkshire Terrier Club of America:
Yorkshire Terrier Club of America About The Club
As far as shots go, puppies should not start their shots until they are 9-10 weeks old. They get immunities from their mother by nursing which will interfere with vaccinations given too soon after weaning. They can be completely unprotected from deadly diseases.