Some wet food is already formulated for all ages, but depending on what you plan on feeding for wet, the best thing to do is check on the label of the stuff you are feeding your kitten right now. I know that EVO and Avoderm are all-ages for sure, whereas I am not sure about the others. Mostly, as with all canned food, you want to make sure it is a complete source of nutrition (for example, Merrick's wet is specifically marked as being a "supplement" food, not a complete source of nutrition), and it should be enough to keep a kitten healthy. Kittens should be fed more often than adult cats, but around the six month mark you can start transitioning them to regular meals, though they might get a bit more food per feeding than the adults would. At seven months, the kitten you are planning on adopting can be put on a two meal schedule if that's what the others are currently on.

Kittens need their combo vaccine (FVRCPC) starting at 6 or 8 weeks and it is a series of 3 shots, with 2 or 4 week intervals in between. This is essential for building a healthy immune system, so no you cannot delay them or what would be the point of vaccinating? Rabies would not be necessary for an indoor only cat, nor feline leukemia. I do not vaccinate for these if indoor-only because of the unnecessary risk of side effects. But this does mean your cat must remain indoor only. Definitely do de-worming and stool tests for parasites. Vaccines are -not- expensive. If you have to ask about cost concerns on here, then definitely do not get two cats. If you have to ask about whether or not you can delay vaccinations or not give them at all, please consider not getting a cat. A FVRCPC shot or a vet visit cost about the same amount as a high quality bag of cat food, so if you can't afford that, please don't get a cat and then give it mediocre care.