I think its based on the owner, and the breed of dog. I think someone would be crazy to have more 4 australian shepherds, or any other very high energy dog.
And about cats, me and my family have 23 cats. They are all very well taken care of, their areas are very sanitary, they get veterinary care, they are fed high quality foods. The city I live in has THE highest euthanisia rate for the state of California, and has one of the top 5 euthanasia rates in the U.S. There are tons of cat rescues, but these rescues are FILLED to the brim with cats...>There are feral, stray, and kittens running everywhere in this city. Nobody seems to understand the importance of fixing their cats, and then they take the kittens to the SPCA< or dump them on someones property. We take in a lot of unwanted cats for that reason. And we are not the only people who have taken in the strays, and who have helped spay and neuter and release ferals (We have spayed several ferals who have been creating more and more stray/feral kittens). Our city actually raised the limit one person can have of cats from 4, to 19. And its not like they even care if someone has more...because we are taking these strays off the streets and giving them a home. (Every cat rescuer and volunteer I know has atleast 10 cats, if not more.).
On to dogs. We have 12, as you can see in my sig. Most are very low energy dogs, and 1-2 hours of play in the backyard tends to be good enough for them (Ages are:11,9,7,7,6,3,3,2,2,2, and two dogs who are older than 6 but age is unknown)..So most of my dogs are considered elderly. But I give the dogs who want and need more exercise as much as they want. They are fed a good food,they were all basic obedience trained, they get out of the house often (As much as we can, atleast 4-5 times a week). And they spend most of the day with atleast one human. I only work part time, and haven't started college yet..and me and my friends hang out at my house..so the dogs are with me all day long, and with my mom all night long when she gets home from work.
SO I will say again, putting money aside, it is STILL based on the human caretaker, and the breed and age of dog/s the owner has.