Litter pan (if inside)
Water bottle and Water Bottle Brush
Litter (if inside)
Grooming supplies (nail clippers, brushes, combs)
Rabbit run, playpen or harness and leash (if the rabbit is kept outside)
Pet carrier (a box can be used for transportation to the breeder and back, but you should have one on hand in case of an emergency visit to the vet or if you want to bring your rabbit anywhere)
Newspaper (usually free)
Beds and Hide-a-ways (optional)
All this usually comes to a grand total of over $200 for just one pet. But the monthly or bi-monthly costs are very low. For my pet rabbit, I would spend about $30-$40 a month on her before I started buying in bulk with the rabbitry.
A word about buying in bulk: 25-50lb bags of feed and hay can go bad really fast if there is only one rabbit consuming it. Feeding mold to a rabbit can be very fatal.