http://www.marshallpet.com/ferrets.aspMarshall Farms represents a very well known mass breeder of ferrets. They sell them not only to pet stores, but to laboratories. Some common problems with such breeders is that the ferrets are not necessarily bred dependant upon the health history of their ancestors, and because they are weaned far too young for their age, and shipped in substandard conditions. Most ferrets are Marshall farms, or other mass breeders that have acquired the same identification as Marshalls...two small blue or black dots on the right ear of the ferret to represent that the ferret has been neutered/spayed and descented. Neutering and spaying a ferret at a very young age has can have long term growth effects. but unfortunately is still legal in the US.
I could tell you to avoid these Marshalls ferrets like the plague, but then you may miss out on a wonderful pet, and in some areas of the country it would be very very hard to find a ferret that is not a Marshalls. Marshalls pets (and other mass breeders) may have a higher mortality rate due to common ferret diseases like insulinoma and adrenal disease.
I, myself, have a Marshall's ferret rescue. I love her. Wouldn't trade her for the world. Just be aware that ferrets that do not come from a true small ferret breeder that tries to breed for health and temperament may not live as long, or be prone to long-term health problems. Or they may not have a single problem and live for years and years.
My recommendation is to education yourself about the care and well-being of a ferret, and the trials and tribulations of having a pet ferret before you consider any ferret..rescue, Marshall's, or otherwise.