Welcome! It’s great that you are doing your research, and wonderful that you are thinking of rescuing.
I think my biggest tip of a free-roam bun would be to start out with a pen-set up, so your bun has an area that is just “theirs” with their hay, litter box, water bowl, a hide, and some toys. It helps the bun to settle in to have them confined to the pen for a few days to a week, depending on the bun’s temperament (they will usually let you know when they are ready to explore). Once they are comfortable with their pen and their litter box habits are in order, you can start allowing them to explore a bunny proofed area. It can also help to start smaller with this, and gradually increase the amount of space and the amount of time they are allowed to roam. This will help you make sure your bunny-proofing is up to par, and help with litter training.
Some buns are not good candidates for 100% free roam, because they find ways to get themselves into trouble no matter how well you bunny-proof. That’s why the pen set-up is great, because the bun can be contained when they aren’t supervised. Most bunnies who get ample exercise think of their pen (or condo) as their burrow and really do enjoy resting in their safe space.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.