@penny1960 that was very well put about adopting a pet.
I'd like to add also that one of the new bi-products of purebred breeding is that degenerative myelopathy is becoming more well known in many large breed and yes, even small breed dogs. The disease is genetic in nature and there is reliable testing for the gene. Having the gene isn't a guarantee that your dog will develop the condition but it does raise the chances of it occuring and would be prevalent in any puppies produced if your dog breeds with another dog that has the gene.
Our 9 year old Australian Cattle Dog has developed it. We thought about getting another ACD but now we won't as they are finding more instances of the S0D1 (I think that is the gene responsible, but please don't quote me) gene in tested animals.It's heartbreaking to watch him slowly decline like a person with severe MS, which this disease is very much like.
Am I promoting mix breed dogs over purebreds? No. There are a lot of good pure bred dogs out there. Just be aware of the genetic problems any breed of animal you are looking at so you are aware of what you may be facing down the line.