A puppy mill “broker” is a pet dealer engaged in the business of re-selling puppies who were bred elsewhere. Unlike retail pet stores, brokers are middleman dealers who obtain puppies from breeders and puppy mills, and then transport and resell them. Brokers typically sell puppies to pet stores, but sometimes to research facilities, often travelling great distances to do so. In some cases the term is also used loosely to describe people who re-sell litters directly to the public that they themselves did not produce, for example, by posing at the original breeder and selling them through websites or classified ads.
The Humane Society of the United States, "Puppy Mill Brokers" (2013). PUPPY MILL REPORTS. 6.