I have pets from all those places- including other. Not so sure about the mill/byb thing- who judges whether a breeder is legit or not? A very conscientious breeder can look pretty sloppy beside an even more conscientious breeder. And technically, petstore animals could often be said to come from a mill, so I think that option is quite ambiguous.
But of my pets-
2 dogs were strays, 2 from a breeder,
2 cats were foster offspring, 1 was stray, 1 was private rescue
both my pigs were from petstores
rabbit breeder
rats- 2 from breeder, 2 from feeder breeder, 1 rescue, 1 from feeder bin at petstore, and two private rescue
Hamsters- 3 petstore, 1 private rescue, 1 breeder, 1 rescue offspring, 5 we bred
Gerbils- 2 private rescue, 3 offspring of these
That's pretty much it. I do take in a lot of private rescues as I have that reputation. ;)