As a breeder I do ask that question. A Yorkie should not be left alone for long periods of time; puppy OR adult. They are very social and LOVE company. If somone has a Yorkie or another toy breed, I may consider it depending...
I work out of the home full time and I pay someone to come and let me dogs out and check on them once a day. So they are alone for 3.5 hrs at most. They are not an only dog, they have eachother to keep themselves company. This is just my opinion which is based on my experience. I just want the best for my puppies and what them to go to a home like mine or better. Nothing less.