I have a fussy male BP that refused frozen thaw for a long time.
So when he would start his fasts sometimes I would end up with a feeder rat and no where for it to go. Most of my pet rats were feeders. There's honestly very little difference between most feeder rats and 'fancy' rats unless you find a show breeder. It boils down to how they're raised.
A very young rat like that is pretty easy to train. They can be very food motivated. Some potty train to pee in a litter box. Poop sometimes still gets left wherever.
My last failed feeder rat knew his name. He would take your finger and lead you back to his bed for snuggle time if he didn't want outside time. And my partner's favorite was holding his arms out so the ratty would run across his shoulders and to his other arm for treats.
They can still just be super affectionate if you don't have time for dedicated training.
Pretty much all rats do sadly carry a specific strain of micoplasma. So they are prone to respiratory infections when it acts up. Keeping a clean, draft free habitat and not using harsh chemicals nearby is best. Sometimes you can still end up with a quickly developing pneumonia though and that's what can be difficult.