RSPCA Bury and Oldham have a mobile vet clinic that provides low-cost vaccinations, health checks, worming, flea treatment, and micro-chipping within the community, but there's been a furious debate on Facebook about whether people who can't afford the full cost of treatment should be allowed pets.
Brent at KC Dog Blog in the US has an extended rebuttal of this kind of attitude:
As an animal welfare community, we have somehow gotten in our minds that we need to try to punish people for not altering their pets -- and consider them 'not worthy' of pet ownership if they don't. So instead of taking the time to educate, and to be part of the community and being people who want to help, we become the people trying to take their pets away.
And if the animal welfare continues to create a divide between itself and various communities, we will fail. As Donna notes in the post: "To decrease euthanasia rates and curb irresponsible ownership, we need proactive, cost effective solutions to embrace the human-animal bond, rather than tear it down."
Sometimes animals do have to be taken away from owners who can't or won't care for them properly even with support. Most low-income pet owners are not like that; they do love their pets and want to do the right thing. However if you really are short of cash the temptation is always to put your head in the sand and hope your cat won't get pregnant before you can save up the money to get her spayed, or that your puppy won't catch anything nasty if she's not vaccinated. If we simply decree that these people shouldn't have pets we're removing a huge number of homes where unwanted pets could go and creating more homeless pets from those they already own.
Animals are always going to be relatively cheap to acquire, because two cats, dogs or rabbits can produce more of themselves at little or no cost unless something goes terribly wrong medically (at which point it becomes hideously expensive, but it is TOO LATE to lecture the owners about their shortcomings). Attempt to ban ordinary, good owners from keeping animals and they will simply hope not to get caught.
Veterinary support (with some strings and a requirement that the owner does contribute something towards the cost) are an essential element of an effective strategy to end killing of unwanted animals in shelters.