We have four cats, all adopted - no one cared we didn't have a cat flap, but because I work from home that's never been an issue.
However, you must have at least one litter tray - cats, even 'outdoor' cats need that option. We only have two trays, one upstairs, one downstairs, because when we gave them more they only used those two, so we took the others away.
You will notice your cat/s are quickly in a routine of both toileting and going in/out if you're around to let them out. There is always a variety of poo in our litter trays in the evening/morning, so it appears they prefer to use the 'inside toilet' rather than the 'outside' options, but you can't guarantee to control where your cat toilets like you can with a dog, or another domestic animal which is caged, unfortunately.
Intrigued by the black and white cat comment about them being more highly strung - all of ours are black and white (deliberately so - they are around 65% more difficult to rehome because people like 'pretty' cats of different colours) and a bunch of four, unrelated, more chilled cats you could not hope to meet! In fact, I've seen the opposite in articles - that if you want a laid-back cat get a black and white one!
Wouldn't be without any of them (and we were never 'cat people' until we rehomed the first two 10 years ago!). Yes, they tie you to a certain extent, and you have to put the time in, play with them, interact with them, get to know them and what works for them, but when an adopted cat looks at you and says with their eyes/behaviour "You're my mum - I love you" there's nothing else like it!" (Can't seem to attach more than 3 photos, so here are 3 of them!)