Hi, welcome to YT.  I applaud you for taking the time to think this out and make the right decision and also seek advise from other yorkie owners.     
I recently met someone who had a 10 yr old 3-lb yorkie and said she was healthy as a horse and never sick a day.  I think it probably depends on the breeder and quality of the dogs he/she is breeding.   
I have a 13 lb yorkie and I have had several people tell me she is the cutest yorkie they have ever seen.  A girl at Petsmart told me yesterday that she is out looking for a yorkie that is Daisy's size because she thinks Daisy is so beautiful.  I am so happy with my "big girl", but if it was me I don't think I would be comfortable with one that tiny, I would be afraid I would step on it.     
				__________________  RIP My Sweet Darling Angel Daisy 08/09/03 - 10/02/15, RIP My Sweet Baby Boy Teddy Bear 02/01/04 - 02/11/16  Photos HERE     |