Picking up every cute little thing and bringing it home isn't exactly ideal for keeping a clean home, after all. Chad figures that it is a reasonable price to pay. The little cute things need to be rescued, and who better than him? They must have been placed in his path for a reason.
Besides, they make a great audience for his guitar-playing. Especially the kittens. They liked to curl up in his lap and purr whenever he plays. To Chad, it is the best feeling in the world.
He often finds himself short on funds. All the food, toys, blankets, milk, kitty litter, and other accessories build up fairly quickly. He doesn't mind, though. Cutting meat out of his diet makes a big enough dent in his expenses for him to be able to afford the extra residents. It's an inconvenience, but certainly not intolerable. He feels that it's helped him improve himself, anyway.
Once, Ichigo asked him why he even bothered. If they died without him, it would simply be nature at work. It wasn't Chad's fault.
"I made a promise," was his only response.