I hope you have put alot of thought into getting a yorkie for a young child who is only 4 years old. I personally do not agree with getting a dog for a child as they are not toys and need ALOT of care and attention and cost alot of money to look after.
I hope today goes well and you find your little puppy you are looking for.
Its such an exciting time getting a puppy. My Poppy is 6weeks old and she is ALOT of work and i have spent sooooo much on her. She is worth every second tho. Kepp us all updated on how it goes today
Good luck
xxx