I've had pet rats almost all my life, but it started because of a snake. I literally grew up with a "red-tail" boa, and when I was in 5th or 6th grade, I found out my dad had had a pet rat as a boy, so naturally, I wanted one too. The one I picked out happened to be pregnant already, and I somehow convinced my parents that I should just raise Huggy's food for him. I usually had 3 or 4 pet rats and about the same number of feeders at a time, and when I was running out of feeders, I'd just breed some of the pet ones. I'd usually end up with extras, which I'd sell to the pet store.
Even after my dad sold Huggy (which I will never forgive him for, :() I kept pet rats, but purposely didn't replace any that passed, as I knew I'd be leaving for college. I lasted 1 semester before I snuck 2 rats and 2 hamsters into my room, they lived until right before I graduated. I didn't have any rodents for about 5 years, as my boyfriend had bad allergies and I learned about the joys of F/T, so didn't need live feeders. I started up again with them this past November, as said BF and I broke up, and now I'm breeding on a larger scale, not only for my own snakes, but to make some extra cash selling to some friends.
Even now though, I have favourites that I consider pets, and ones that I just use as breeders. They are all treated the same, the only difference being that the pet ones get taken out for cuddles. :)