Besides, would the owner know that you plan on using the ferrets as feeders? I'd be pissed if I found out that the pet I thought was going to a loving home was actually used as snake food. Don't get me wrong- I know that snakes need to eat and I have no problem feeding my ball python her f/t rats. But I would never go on craigslist and "adopt" rats just to turn around and feed them to my snake. I think that is unfair to the previous owner. If you are going to go through with it I think you should be clear about your intentions.
This. It's best not to be deceitful or you'll give more news for PETA to scream about. There should be a line between feeding animals that were clearly born and bred to be feeders vs an animal that was raised as a pet.
1.0 Ball Python (Mystic Potion) Tapioca
0.1 Northern Pine Snake - Impa
0.1 Russian Rat Snake (Melanistic) Kallari (RIP)