How many cats are  in their home, and were you able to see them all?  Too m any cats should be a red flag, regardless of the conditions.  Too many cats means there is NO possible way all of the cats and kittens get individual attention on a regular basis.  It is simply impossible.  Regardless of how much affection you see them give the cats while visiting, your mind probably questions that too many cats seems a bit ridiculous. you're right.  Realize that a breeders will always have more cats than the average person, but keep reality in perspective.

Maine coons should be raised around all the daily activities of people, in their bedrooms, kitchen, around TVs, etc...some cats may be confined (such as whole males), but good breeders have a large place/room for the boys where they each have access to a window at any given time and enough room to jump and play, some even have TVs for their entertainment!

And, if their house is spotless consider how much time that takes, and what that takes away from the attention the cats get.  We aren't saying that clean houses are not possible, but we believe it is just as important that the home is well kept/sanitary, has less than a few dozen cats and ALL the cats appear healthy.  Runny noses and eyes are NOT typical of a good cattery.