People who are serious about breeding yorkies usually find a mentor who will work with them and teach them about breeding. I don't believe breeding should be something done as a business venture, but something you actually feel compelled to do because you love the breed. Choosing puppies to breed would be risky because you have no way of knowing if they will be within standard as adult, and only those yorkies that fall in the standard range should be bred. We already have too many unhealthy dogs being bred; and unless you are willing to take the time and effort to become a quality breeder, I hope you reconsider. There are much easier ways to earn living; breeders are on call 24/7. Here's a link that gives some of the difference between a backyard breeder and a responsible breeder.
Lawrence County Humane Society Abuse and Adoption Center I do recommend you read the breeders forum, there are many different threads that will give you lots of good advise.