Can't speak from kittenhood, as mine were around 1 and 2 when they arrived. But apparently starting from kittenhood is even easier as they don't know the difference. Would you be keeping it indoors by choice or necessity? I feel like if it's going to be a constant 'don't let the cat out!' then that would be annoying, for you and them. With mine, there is nowhere for them to go, so it's just how it is.
How big is your house? The smaller the house the more effort you have to put into keeping them happy. I've got 2 in a 2 bed flat. It is slightly less than ideal, but nobody's gone mad. Aside from the one that's already mad.
Logistically:
Trays. 1 per cat + 1 is standard, though I just have two because of space, and because I'm at home most of the time to scoop on demand. You will be surprised at their excretion levels.
Toys/Interaction. They do need it. But toys are cheap and it's no biggie, plus they do invent their own games.
Windows. Especially if you're at ground level, because it is a pain in the ass in the summer. I'm on an upper floor and do open windows, because they like it, I like it, and I trust them not to be idiots. Obviously I'll regret this massively if something happens.
They do seem to bond with humans more when they're indoors, which is nice in lots of ways but also means you're more responsible for them than with an outdoor cat. They need chatting to, and paying attention, and in The Lamb's case a lengthy bedtime patting routine.
I do think that some kind of outside is helpful - mine have a concrete balcony walkway thing and that helps, they can sit on the wall, smell the breeze, gawp at things. I have a pot of grass out there for them to munch on, which stops them doesn't stop them eating the plants.
I'd consider two, if your space can handle it. Especially if kittens as they can play together.
Importantly, cat personalities vary and can be unexpected. The madcat was my worry, because she is Very Active. The lamb was supposed to be a 'perfectly happy indoor lap cat' as she has a disability. The madcat will sit outside for a minute until she sees anything move, then wail and bolt back in to happily carry on with her parkour routine in the living room. The lamb has made several escape attempts, and I feel regular and mounting guilt about it.
erm, that's probably enough to be getting on with. Questions?