It's odd, but we're all making assumptions here. We don't know if he passes all the legal requirements for whatever he is advertising for because he doesn't mention exactly why he wants these animals. One can always ask him if they're interested. He does mention that he will slaughter the animal on the property, so I don't think he's trying to hide anything from the animals' owners. I'm betting he's a butcher or meat processor trying to make a buck and get some free meat, too.
ETA: Some butchers and processors do come to people's homes/properties to slaughter their animals.