Mousers/barn cats are usually born to other Mousers/barn cats, because many of those skills are taught by the mother. At least that's what I've always been told. Not something I'm experienced with. If not I know of a rescue that sells kittens and young cats for 20$, or at least used to. But they are all fixed.
I have a rescue cat already. He too is fixed but he is not the best hunter / killer. He might be getting better but so far his strong suit is begging.