Only have 2 (unless you want to count Keno as a cat - she thinks she is)
The most I've had is 9 (I think) - was when I had Lady (rex) and her 6 kittens and 2 other HHPs.
Usually I only count adult cats that are not leaving - never kittens cause they were gone to new homes by 4 - 5 months old. I put my personal limit to never more then 6 adult cats (not counting litters).
I only have 2. I can't imagine having more because I can bearly keep up with the litter box, vacuuming, feeding, cleaning up hair balls, playing, lovings and brushings for just them. The 2 cats I have are very time consuming and I can't see myself trying to stretch myself and my time between any more.
We currently have 20 cats/kittens living inside of our house. John and I have our "original" group (Tabitha, Spooky, Leo, Sasha & Olive), little Spike, new momma Missy, Sasha's 5 kittens + 2 "adopted kittens", and Missy's 4 kittens... plus John's dad's 2 cats Stranger & Grabat (Stranger is outside most of the day though)... and we've got at least one barn cat.
When it's all said and done we'll have Tabby, Spooky, Leo, Sasha, Spike, and we're keeping 2 kittens. Missy and most of the kittens are going to new homes and unfortunately Olive is also going to a new home due to agression issues... she's going to a great home this weekend with no other cats, which is what she needs.
At my most I had 11 (including fosters) in my house. Which was a bit crazy...but tons of love (and tons of poop!!). I'm back to just my 2 babies now...i hope when I have more space to get a few more though!!