If you want to eventually breed Yorkies, you must start at the very beginning and learn everything you can about the breed so you can do it responsibly. As the others have pointed out, there is no such thing as a "teacup" Yorkie so you've learned your first lesson.
I'd suggest going to some shows and trying to meet Yorkie breeders to learn everything you possibly can before buying a Yorkie. You need to start with a Yorkie who is a great representation of the breed standard. It takes an experienced breeder to be able to evaluate puppies.
Here is a schedule of shows by state:
InfoDog Dog Show Calendar
I don't know what your financial situation is, but you need to make sure you've got a considerable amount of money set aside for veterinary bills for health testing parents, ultrasounds, c-sections, etc. Toy breeds like Yorkies are at a much higher risk from pregnancy and delivery and complications are common.
A reputable breeder always gives a health guarantee so you will also need money for veterinary expenses should you produce a puppy with a liver shunt, for instance. Did you know that Yorkies are 36 times more likely to have a liver shunt than all other breeds combined? Surgery to correct a shunt runs into the thousands. Luxating patellas are also hereditary in Yorkies. The Orthopedic Foundation of America ranks Yorkies #4 in cases of luxating patellas. Again, surgery to correct them runs about $2,500 and up.
You will also need a flexible work schedule if you are now working full time. You will have to take time off when your Yorkie is due to give birth in case there are problems. Mothers sometimes don't have enough milk, reject puppies or even die and you would have to bottle feed puppies around the clock.
Becoming a responsible breeder is a huge responsibility. You have taken the right first step by asking questions.