Here is a chart about breeding. If you take two pets and breed just for the experience of having a litter, you are a backyard breeder and IMO you are risking a lot. No one should breed unless they know the background of both parents AND both parents meet the breed standard. Too many unhealthy and odd looking Yorkies are born b/c people don't know what they are doing.
I am also totally against puppy mills AND large commercial breeders (though several people on here continue buying from them) You may end up with a cute pup, but the parents are left behind in awful living arrangements.
http://www.shilohshepherds.com/puppy...erMatrixv4.htm