Well, I've adopted both kittens and cats throughout the years. If you want to adopt a feline most people do kittens because you can raise them however you want and make all those decisions. However, if you really want to "save" a cat, then get an adult because there are more of those available, and they put them to sleep often. If the kitten is too young and no one is home all day, that could be difficult unless you have a safe area for them to keep them all day. Although, kittens needs a lot of personal attention (especially if they are young). For me, I have a lot of chords around the house my kitten chews all day long so I have to keep him in the bathroom. They can get into trouble easily. I personally only do indoor cats because they are safer inside, no cars to run them over. No cat fights, dog fights, they could get lost or many many other dangerous things. I've had rabbits and birds with cats but they were in cages, I'm not sure how you keep yours. Breed is up to you. Its nice to let them have a buddy to play with, but cats can entertain themselves, also up to you.
For medical things, you have to get vaccinations for rabies and leukemia, have to get them spayed/neutered, and declawed if you believe in that sort of thing (I think its fine). Other checkups as well, your local vet can tell you. Its not that expensive.
Owned/Rescued cats my whole life.