Outside of a mommy with kittens, the most I have had at one time is 4. There was a lot of litter box scooping and we used a lot of lint rollers.
Fleas, etc were never a problem as none of them ever went outside except to go to the vet and the time I tried to take 2 of them out to play on a harness (It didn't go so well).
We have been down to 2 cats for awhile now, and I am enjoying having time to do something other that combing and cleaning litter boxes but it isn't going to last.
My husband filled out adoption papers for a Persian at a Persian rescue center. We haven't heard back from them yet, but the morning after he filled it out online, there was an "adoption pending" notice on Angles picture.