Whilst it is important you do seem to be focusing an awful lot on the finance issue on this thread. There is so much more to 'rescuing' than this, although that part is vital to the survival of any rescue, big or small.
Is there any reason why you can't just start by helping one or two rabbits and see how you go? Personally I think it would be foolhardy to leap straight in without having done any rescuing at all, either of your own or working as a full on volunteer doing fostering for another rescue maybe.
Before I started operating as a rescue proper, I volunteered for two years at one rescue atleast one regular evening a week and every Sunday for a whole 18 months. I ran the volunteers and worked very closely with the other folks doing interviewing of potential new owners, cleaning out, selling supplies, giving advice, fostering and bonding. I then moved to another rescue and ended up doing the rabbit rehoming with other core members of the team after starting out as a foster carer.
It has been a long hard slog and despite saying I'd never rescue myself, have ended up doing so. I haven't had a holiday in 4 years, hardly have a night out, am like the walking dead sometimes, when I am ill and still have to keep going.
This week alone, I have had 5 calls from people wanting to 'get rid' of their rabbits and I don't have anywhere to put them. I have a waiting list and have to turn people away knowing that there is very little chance of most of the people waiting until I can help. This is far worse for bigger places than me that will get many, many calls daily and often get abused for the enivitable 'we're full'.
I often have to say no to people that want to adopt because they just don't understand what it takes to care for a rabbit. Not necessarily their fault, but as a responsible rescuer, you have to take hours talking to everyone that calls, when sometimes you don't have enough hours in the day to even wash yourself or eat anything.
I would strongly suggest that you start by assisting a local vet maybe, with the odd stray or cruelty case here and there, and see if you have got what it takes to actually rehome rabbits before you open your doors to lots of rabbits needing help.
Just a few off the things you will need to consider,
how will you manage your time
how will you manage the enquiries about adoptions (phone/e-mail)
Will you have a dedicated phone line
Will you take emergency calls night and day
how will you cope with rabbits dumped on your doorstep
how will you deal with infection control
how will you find new homes - internet, posters, vets, RU.
how far afield will you rehome
will you do all the homechecking yourself
have you decided upon your rehoming criteria
how will you do all of the bondings for all of the single bunnies you rehome
how will you cope if someone who adopted a rabbit from you needs to return it - how long will you keep a space open after the rabbit goes home
how will you create the right form? registration forms, rabbit handover forms, adoption forms, rehoming information, educational information on what happens when the bunnies go home (for new owners)
will you have volunteers to help you - will you be able to insure them and the visitors to your home.
There is so much more, you get the idea.
I know I sound like I am being negative, but from my own experience, I would have to say 8 months ago despite a number of years working at rescues, at a vets, and having many rabbits pass through our doors, I was not ready to run a rescue. Now for some reason, I am running a rescue and it's working so far.
Take your time to do your homework, maybe associate yourself with a rescue near you and learn how they do things. There is definitely enough work for you to open a rescue, but you need to make sure that you make it a really good one.
Good luck
Helen
p.s. you don't have to be a charity to rescue. Why not start out small and then if you feel you can grow, you can register.