One thing taht would scare me about cat sitting would be escapes, especially with 23 Cats where you cant count heads as so many are hiding from you.
And litterboxes for 23 Cats , the taking in and bringing out is a headache , I know from my 8 Found Cats.
And with Multi Cat Houeshlds making sure that everyone is fed, and that some Cats arent getting more than thier share!!!
Good Luck with Your Mew Career!!!