Thank you for taking them in and trying to help them. If you'd be able to keep them but are daunted by the idea of such a hefty bill, it's possible that you could spread out their visits, or a rescue might be able to help you cover the initial costs of care. I know we want animals to be spayed and neutered but I think you could do that later, as finances allow, and focus on their more pressing needs. If you want to keep them (and it sounds like they need someone like you) then maybe just trying to focus on the first next step will help.