When I was a child, we had 9 cats at one point but we lived out in the country and they had loads of fields to roam.
When DH and I bought our first house, we adopted two kittens, a tortie and white and a dilute tortie and white. They were indoor girls as I'd had way too many cats killed on the roads in my younger days. One lived to 3 months shy of 17, the other to 3 months over 17.
I called them our 'planned cats' but we also had two 'accidents'!! A gorgeous ginger boy started visiting, with the most massive set of nuts I have ever seen on a cat!! He stuck around, so we had him neutered, and took him in. We had a wonderful 9 years with him, but he was a fighter (he was indoor/outdoor). He contracted FIV and he died aged 10 from kidney failure.
Our 4th was a blue tabby. He had been a regular visitor since he was a small kitten, as his owners neglected him, and in the end moved house and left him and a tabby behind - hateful fuckers. The tabby found himself a home and we adopted Oscar, after he was hit by a car and needed a lot of vet attention, which we paid for no problem, and when we moved house, he came with us.
He died suddenly aged 14. He loved to sleep on a 6ft tall cabinet in our garage, and I found him passed away in his favourite spot.
We lost our last three cats in the space of 11 months and it was devastating, but we soon were found by a stray boy, who lived to be, we think, at least 20.
We then adopted two tortie and white girls (who don't like each other but that's another story lol!)
I am constantly tempted to adopt a 3rd cat because we reckon that, if our younger girl had a playmate, she wouldn't torture our older girl so much!!
So, if you can afford food, litter, insurance and vet fees, and you have room for them - have as many cats as you like!! It has all got so expensive, so that's a consideration.
I always say, watch this space, and don't be surprised if I acquire another one lol!