I have two rabbits (Flopsy and Mopsy) who I love and highly recommend. (To answer the obvious question, they're both girls and they're both spayed 😉 )
Anyway, they're great med school pets because they're active at dawn and dusk and less active during the day, so they don't mind not having people around. Having two of them also helps, since they've bonded and they play with each other when they get bored.
They're really cheap (I probably spend less than $20/month on them, mostly for litter, timothy hay, and pellets plus $100/year for a vet check-up). We share oatmeal and veggies with them, which doesn't add much cost wise because our veggies had a bad habit of going bad before we could finish eating them. For toys, they love abandoned cylinder containers (oatmeal and raisin containers), toilet paper rolls, etc. We tried buying them fancy pet store toys, but they weren't interested at all. Ditto with treats--they love raisins, bananas, and strawberry tops, but don't really like store bought rabbit treats. So yeah, very cheap pets.
They take up a small amount of space in an apartment (we built them a cage out of those wire stackable shelf squares that you buy at Target). They're neat--they'll use a litter box quite well
My one caveat is to make sure you get rabbits that are well socialized. My wife has been working at an animal shelter, and the rabbits definitely vary a lot. If you get a well-socialized rabbit, they can be very friendly to you, but poorly socialized rabbits will spray urine, bite, etc.
Overall though, rabbits are a great pet for us, and I highly recommend them.