To me, harnesses are not optional for yorkies. Yorkies have delicate tracheas and walking them on a collar can damage them. I would suggest getting an inexpensive harness to start out with and once your pup is full grown, invest in a leather Buddy Belt. They are great and come in lots of cute colors
As for breeding, you are going to get a lot of heck for wanting to breed. I would definitely suggest that you neuter your pup if you want a healthy pet. A male that has been bred before will mark, hump and search for females. They are more likely to attempt to run away because they can smell females in heat in the area. To me, it's not worth it to have an unneutered male in my home. My male is a family member to me... Not a breeding machine.