Stray and homeless dogs often end up reproducing for the profit of puppy mills.
Dogs live in terrible conditions with inadequate veterinary care, food and shelter. Many animals that end up in shelters are purebred animals from ‘back yard breeders’ and puppy mills.
Often dogs and cats purchased on sites such as kijiji are not from reputable breeders. By avoiding these sites, and going through an established breeder or your local shelter such as Bide Awhile, you will be able to find an animal that has been spayed or neutered and is healthy.
Here is a helpful link with more information: