Rabbits will need expensive treatments as they get older, because they’re not very robust animals. Vet bills can get crazy really quickly, because rabbits are considered exotic animals. They need treatment from specialised vets. So I’d advice an insurance, or alternatively: a monthly savings plan.
Compare insurance policies and see which one fits your situation. Some insurances do cover spays/neuters, others don’t. Answer the following questions for youself, and choose which option is best for your situation:
Is the rabbit you’re adopting already spayed/neutered? This is absolutely neccessary for their health and will be one of the highest initial costs. Reasons for the procedure: intact females will develop a very high chance of cancer in their ladyparts, and intact males become so hormone-crazed that they get agressive and will start to spray urine everywhere.
How old is the rabbit? Younger rabbits are relatively cheap in maintenance. They need a spay/neuter and their (semi-)annual vaccinations. Older rabbits may develop problems with teeth, urinary system or tumors. Vet bills can go through the roof if you’re unprepared, even simple dental work is expensive, as rabbits need a specialised vet.
If applicable: do you know anything about the conditions in which the rabbit was kept before you adopted it? Wrong nutrition or wrong housing can lead to several pre-existing health problems. To name a few: obesity and/or gut bacteria problems due to poor nutrition (too many starches&sugars from grains, not enough fiber in diet), sore hocks or feet ulcers due to bad cage flooring, mites or fleas due to contamination between rabbits. Be sure to get your rabbit checked by a vet specialised in rabbits as soon as you adopt him/her.
That sounds quite doom&gloom above, but what I meant to say was: they’re great pets, but oh so fragile. Prepare well, read up, find a rabbit-specialised vet and you may avoid some nasty expensive surprises.