There is no single way that fostering works, it is an individual agreement between a fosterer and a rescue which will vary from place to place. Some rescues will provide accommodation, food etc, others will only be able to use those offering their own accommodation. Most will cover vets bills although you may need to pay up front and be reimbursed. Some I will pay for food, hay etc, others will expect the fosterer to be responsible for those day to day issues. Some will have all their bunnies out in foster homes, others will only use them for special occasions e.g. Where rabbits are not ready for rehoming due to obesity, illness, birth, behavioural problems, or just as an emergency overflow. Mostly the rescue will still be respnsible for the decisions about the animal incuding when and to where it will be rehomed. Your best bet is to get in contact with a local rescue, ask if they use/need fosterers and have a chat about how it works for them. Don't be offended if they say no, some rescues like to keep all their animals on one site and/or can't afford too manage if they take on additional buns which are fostered out but for which they are still ultimately responsible. Good luck!