I have a hard time keeping the litter clean enough with just a few cats around (can't stand litter box smells). There is no way I'd ever end up with more than a couple resident cats unless I lost my sense of smell LOL.
Oh I found a way to cure the cat that seemed to potty just over the outside edge of the litter box - put her in a small cage with a bed next to the litter box - she learned fast to NOT potty on her bed. Now she runs free and she does a great job in the litter box - never misses.
Could you imagine cleaning that many litter boxes? I am sure all of her cats are very well behaved and never mark or miss the litter box either. I hope she owns stock in febreeze. peeeeeewwww