The person down the street 'selling' dogs is breeding for "money". I.E. backyard breeder, has no dog in the game, no pun intended, so they could care less if the dogs they are breeding 'just for money' have hereditary markers or not. First of all they would never spend the money to find out. And if they did they surely would not stop breeding them because that would mean they would have to buy 2 more to keep on making money. :(
They rarely or never belong to a breed club to even be educated about the breed or be aware of what testing is available. But then again, a breed, all breed club, and/or specialty sporting club wouldn't be rushing to put out the welcome mat for those that breed for money-backyard breeder.
The person who is going to know the most and cares the most about a specific breed and DOES test for markers, donates money for research, participates in open registry testing studies, doesn't breed just for money, etc, is the person that "seriously" emphasis on seriously shows and/or competes with their breed. That's were you will find the information to help you decide which breed you want to welcome into your family.
Not the guy down the street trying to make a couple extra bucks breeding their dogs to buy a new boat and who gives a rats butt if the puppy you pay him for dies at an early age. The property doesn't have to look like a TV ad puppymill but they are one in the same as far as output. Just saying.