Hi! Welcome to YT. The best advice I can give you is to not buy a Yorkie from any pet store or from a broker. To stay away from brokers do not buy sight unseen from the internet unless you do a TON of research and know the breeder you are buying from. A lot of them make themselves out to be breeders but are not, and although there are many GOOD breeders (many even on this site) that will ship you a dog, it's risky unless you truly know what you are doing. Most good breeders will only sell you a dog in person just to prevent this type of thing. They will want to screen you and know your living situation, meet the members of your family, etc. to make sure their dogs go to only the best homes.
Do not buy a Yorkie on price alone. If you want to pay less without sacrificing quality, ask for a larger male. The market conditions have smaller females in greater demand and therefore they fetch a higher price, even from the same lines/litters as the males. I love my little boy! Let the breeder know you are interested in a pet only and not for breeding or show. Loki is from champion lines, but is larger (between 7-8 pounds at 1 year, which is still small IMO) and has floppy ears. If I let him grow out he would have the show coat and coloring, and definately has a great personality and temperament and does not have any hereditary health problems (at least that we are aware of but they tend to show themselves by 1 year). Be wary of the health guarantee. Good breeders will give one - but most require you return the puppy if there is a problem. You will be attached to a pup the minute you take him home - so still make sure the parents are healthy etc. because you don't want to take any chances with their health!
There is so much more. This site is a great resource. There is a breeder forum as well if you have breeding specific questions the breeders are most knowledgeable in that area. Many of the other members have learned a great deal about Yorkies either by learning through mistakes (like buying from a pet store) or by doing extensive research in their own search for a pup.
Let me recommend Loki's breeder. Susan Harasim in Clarendon Hill, IL.
www.stardustyorkies.com She does not sell over the internet - you have to call her. Many of us on this board have her pups. She will be honest with you if you are honest with her. Tell her what you are looking for and she will steer you right. Again, there are also good breeders on this site. They are a good place to start as well. Be prepared for a LOT of questions - breeders do not let go of their pups easily!
Also, a Yorkie is a huge investment time and $ wise. You probably already know this, but it's always good to emphasize. The initial investment is only the beginning of the expenses. Most of our babies are not easily left home alone all day. They cannot hold it all day until they are much older than other bigger dogs would need to be. They need constant human interaction. They take forever to housetrain, but they do get it. When they are puppies they pee every 10 mins and I'm not exaggerating. They need to go to the vet a lot - even a bout of diarhea and they need to get checked out. They require special anesthesia for surgery and often need to have puppy teeth pulled. The smaller ones can get hypoglycemia. They need clothes in the winter. They need the best food because their bodies are so small and sensitive. The smaller ones are not good with kids because of their fragile size, although Loki thinks he IS a kid and kids are his favorite people! And finally they are not lap dogs, they are terriers - or terrors as we like to say!! But you will fall in love with your baby and there is nothing better in the entire world and it makes everything worth it!!!
If you have any questions ASK ASK ASK! This is the place to ask. Good luck finding the perfect baby!!