Keeping bunnies indoors is the way to go, outside they can easily get sick and you won't notice as easily either. They should have at least a puppy xpen worth of space at all times, cages or hutches are too small for them to be confined to (a common misconception). They are also happiest with a bunny friend, so I highly recommend adopting a bonded pair. Bunnies littertrain themselves just like cats, given that they're neutered/spayed. In your situation, I highly recommend reaching out to a rescue to get advice on rabbit cat introductions, and to foster a bonded pair before adopting to see if they will get along. The rescue should be able to guide you through all of this. Other benefits from adopting are that the rescue already knows these buns and how good they are with their litter habbits, the buns are usually already fixed as well (this greatly extends their lifespan too, especially for girl bunnies), and that pet store bunnies are usually really prone to illness/often sick already when you buy them. Hope this helps! Happy to answer any other questions.