It would be great if the breeder has the dam and sire on premises. If she doesn't she should have photos and info on the stud. Don't buy any pup younger than 12 wks, the older the better a good rule of thumb at 12 wks you double the weight and approx. it will give you the adult size. Now not always does that work but it should give you a fairly good idea. I wouldn't breed any female less than 5 lbs. the bigger the better, but try to stay with in the yorkie standard size. Also take in consideration that the poor mom has just delivered pups and not always do they look there best, most of the time they are either shaved or cut low, but again breeder should have some photos of her to share with you on how she looked prior to delivery.Hope this helps.
P.S. she or he should also have pic of there previous pups and as adults so you can have a better idea on how they should come out looking.
