Please help with unexpected vet bill

My cat Possum has an awful abscess on her bottom caused by a bite from another cat or dog, or insect. The vet has just told me it will cost $500 to put her under anaesthetic and clean it up. I am on a pension and cannot afford to pay the bill. Possum is a lovely Somali cat. I chose to rescue her rather than any of her kittens because I thought nobody would take her, the mother cat, about five years ago. She is mostly an indoor cat - I am an animal lover and am taking care of my three horses (fell on bad times, but feel I have a duty to the animals I had during that time) a dog and another cat I rescued. Only an animal person would understand my need to care for these sentient beings, who also give me some quality of life - I live alone and have nobody to help me.

It was very scary and embarrassing yesterday - I thought the consultation would be $75 and some ointment for Possum's bum. I told the vet I had no money but she took that to mean I didn't have any on me at that moment and said I didn't have to pay until after the op, which could cost $500 - but I said I'd have to pay it off (even though that amount would take me six months) - then afterwards, when I said the best I could do was the end of the month (I didn't know how) the practice manager gave me such a dressing down I felt like I'd killed someone - she then had me sign a CentrePay form in case I "took the cat and left town" and then she could take it out of my pension - so in despair I did this crowdfunding, embarrassing myself further, thinking if a lot of my friends paid me five dollars I could get the what turned out to be $532 bill down to a manageable size or paid. Thank you, thank you, thank you - free books (The Hat Blocker) for all backers when I finish it, but that could be a couple of years