There is or was a requirement for how much money a breeder could make in a year even if you had three or less breeding females. I believe it was $500. If you made more than that even with 3 or fewer females and want to sell your pups via petstores, you would have to get a USDA license.
If you want to sell your pups for the petstore market, you must have a USDA Dealers license, either "A"-breeding only or "B"-breeding and brokering (basically buying the pups from either a person having an "A" license or breeding and selling your own pups in which case you would have a "B" license to petstores). The Hunte Corp. does not breed dogs but has a "B" license so it can deal/broker pups from "A" licensed breeders to petstores.
There are also "B' dealers who sell to research facilities. It is my understanding that there are only around 10 doing this. The auctioneers and/or the dog auction facility must also be "B" licensed.
The USDA has many laws about what can and cannot be done which is the Animal Welfare Act. The facilities are inspected but I think it is only once a year. If something is found that is in noncompliance, there is a date given that it must be fixed by and the inspector comes back to inspect again.
One can now look up inspection reports for everyone who is USDA licensed. This includes exhibitors like zoos, circuses, carnivals, etc., carriers and handlers like airlines and transport companies, and research facilities like universities, hospitals, labs, etc.
If one thinks being USDA licensed is so good, just think of the egg farms that were shut down because of human illnesses and the conditions of the facilities.
Not all breeding facilities are like this but reading some of the inspection reports will educate you. Before attending the auctions, I had no idea how breeding dogs lived. I am amazed at the buildings, trailers, barns, etc. that they live in.
It is not only breeders of dogs that need USDA licensed but also cats, rabbits, etc.