Well my expertise is only in fictional assholes and villains but I think some things I know can still be helpful.
-Leave out plenty of fresh clean water that’s easily accessible to him at all times.
-Feed him a proper meal three times daily. Diets vary from dream person to dream person, so make sure you know what he wants before trying to feed him.
-Obviously he’s gonna need a bed.
-Find a good doctor in case he gets sick. Also it’s good to get regular checkups because sometimes things are easily hidden.
-Bathe him regularly so he doesn’t get fleas.
- Uh, something that’ll keep his mind stimulated so he doesn’t just sit around bored all the time.
- Take him outside for walks or fine dining?