Just search online for 'Puppy Scams' and you will begin to understand how big the problem is. The Better Business Bureau maintains a webpage about avoiding pet scams; https://www.bbb.org/northern-alabama/news-events/bbb-scam-alerts/2016/01/how-to-spot-a-puppy-scam2/.
I decided to write about this topic when I saw an article about this a few weeks ago. I realized the same advice that will help you avoid being taken advantage of by these scammers will also help you identify 'pet mills' and avoid patronizing, and supporting them.
Puppy scams involve unscrupulous, dishonest people advertising pets that don't exist, and taking payment for them, then disappearing when you try to pick up the pet. Pet mills are breeding operations that only see dollar signs with fur and four legs. The worst puppy mills operate much like the robber baron factory owners of the 18th century; they keep their 'workers' (otherwise known as pets) in squalid, unsanitary, cramped and crowded conditions focused only on maximizing their bottom line and willing to sacrifice everything else to it.
The first step in avoiding puppy scams, and pet mills is to visit the breeder. This allows you to evaluate their facility and practices first hand so you can be sure you are comfortable with how they do business. If the breeder is reluctant to let you visit be suspicious. If they refuse and instead offer to meet you in a parking lot; run, don't walk, away. The 2nd step is never let money change hands without seeing the pet first hand, or at least make sure you have a way to track and stop the transaction (check or credit card) if needed.
Finally, check some references on the breeder. Don't rely exclusively on reviews on the breeder's website. Signs of a good breeder include membership in a breeding association such as the American Kennel Club. A good breeder will be interested in improving the breed, not just breeding more of them; this means associating with other breeders. Good breeders also have readily available medical record information for their pets, including the parents and offspring. Ideally they should provide this to you before you ask for it. If they say they will send this information to you later be suspicious. Good breeders work with a veterinarian to be sure they aren't simply perpetuating preventable, heritable diseases and problems generation after generation. if they don't have a veterinarian referral ready for you be suspicious.
If you think you've encountered a pet scam or pet mill contact animal control immediately. They will be able to help you. Be careful of your urge to buy the pets and rescue them. You may just end up funding the operation's future, dooming the next generation to the same fate. it will be better to get the authorities involved so they can shut the program down, and rescue the pets through the animal shelter. Along the Wasatch Front there are enough shelters and rescues operating that the chances of finding good homes for the pets, once the news gets out, are much better than if you try to rescue them yourself.