Cats are mostly self-maintained. My dog grew up next to a kitten of the same age, who unfortunately passed away a few months ago.
I've had cats all my life. There's no litter box training - just show them where it is, and they'll handle things from there. I'd suggest an automatic litter box to save yourself a lot of work; I used a
ScoopFree litter box and it was great - change the litter once per month.
Cats can be rather sensitive to what they eat, but it's very important they DO eat. Get it on a stable diet and you should be good to go. They love milk (but are actually lactose intolerant - just like dogs), and will beg for food endlessly.
Expect all furniture, drapes, etc. to be scratched up. Expect the cat to climb on anything and everything - top of fridge, inside of fridge, window curtains & window screens, tables and desks, etc. If you're on the computer, the only place to sleep in the entire house will be your keyboard.
Cats are generally very easy and great pets.