Get a cat. I would say get it 1-2 months before classes start because kittens are cute and you'll want to spend a lot of time with it in the beginning. They're great company. Though if you end up moving later, there is the extra hassle of finding places that allow pets. You'll be studying a lot, and chances are you may end up skipping class and watching vids at home, allowing you to spend more time with your pet.
Pro tips I learned the hard way:
1. Get a scratching post. This is mandatory unless you want him or her to scratch up your bed/couch/anything it can get its little claws on. They tend to prefer the scratching posts (get a medium-large size one, the ones with just a post tend to be wobbly and don't work well) anyways. Reward him for using it, poke/chide him for using anything else.
2. Vacuum. Also essential.
3. Furminator (google/amazon it). Seriously. It'll cut down on the shedding. Don't bother with a brush/etc. Those don't do much. I had a friend profusely thank me because I recommended this. They had tried everything and thought their pet was a hopeless case. I bought them one for Christmas and the pictures they have advertising their product with the loose hair it pulled out next to the dog/cat? No lie. Heh, word of caution. Don't go overboard. I once gave my kitty a bald spot because he was purring so much and liked this, that I didn't realize I had finished getting all the loose fur out. Overboard being 30 minutes.
4. Indoor is great esp since you said your place was big. I liked it because it meant my kitty was basically in quarantine and no diseases/etc from the outside (unless of course I was sloppy and brought them in), and you can snuggle fluffy all you want without wondering if he's been hopping in dumpsters. Also, cats are crepuscular so they'll be sleeping most of the day. And if you keep him/her indoors, you don't need flea meds.
5. If you're really ambitious, you can toilet train you cat and even train him to flush after himself. This will take patience. Google/youtube this. It took me a year (because I started when my cat was way older and I wasn't home all the time) to do this, but if you start early you may be able to get it in a few weeks tops. Pros of this = no having to clean up cat litter, and your cat won't smell like cat litter and track it every where either. This is also why I recommend getting him/her 1-2 months before school starts.
6. Also, before you go overboard with the kitty toys, you may want to try the cheap stuff first. My guy doesn't seem to care for the expensive stuff, but give him shoelaces, my hairbands (there is a constant war with this one because he will open drawers to steal them. I've hidden them in between books, on top of cabinets, underneath papers, on top of my books in the bookshelf, and I have yet to find a place that is cat safe. He can also open doors that aren't locked), bottle caps, etc. he has a field day.
7. Don't feed them according to the manufacturer's instructions. It's usually way too much. I didn't realize this til my cat was getting fat, then I cut back and he's a normal size. Kittens will eat a lot though, so I think it's fine to feed them a bit when they're a kitten. Adult cats, mine is on the bigger size and I only have to feed him 1 can of wet food a day.
Get a cat. They help with stress (which you will have lots of), and when you want to take breaks they love to play with you. Mine has been extra work, but also has given me lots in return. I don't regret it at all. Also, may I recommend you take a peek at your local animal shelter? That's where I got mine and he is super awesome.
Oh, missed your cost question. Hm, I think it was around 50$ when I got him at the animal shelter and that included getting neutered/tapeworm meds/etc. Toys and things to me are a one time cost unless you splurge at Christmas. If we're talking bare minimum, I feed mine 1 can of wet food a day, which is about 0.50$, so 15$ a month for food costs. If you end up doing the litter route that's going to add a lot more. Start up cost for that toilet training, well I'm sure you can amazon it up
. Your start up costs for everything probably will be 200 if you really want to splurge with the amazing cat towers/etc, catnip, litter box, cat litter, the cat, furminator. I always kept extra money in case something went wrong for vet reasons though.
Good luck OP, hope that helps