SPCA Question?! curious?

As you said they are all different, but basically they don't help you with your sick dog. You have to turn it over to them, if they'll accepted, and chances are it will be euthanized, depends on breed, size, etc. They do run clinics couple of times a year for low income people, but like you said, timing wise it may just be at the wrong time and not when you need it. You should try to find a no kill shelter, and see if perhaps they could help you out. I hope there isn't anything major wrong with your dog. Best of luck to both of you!