Please help me feed & vet my cats

Hi! I am a 68 year old disabled lady with a colony of 30 cats and kittens The colony consists of rescues, ferals, throw aways and dumps . I am on social security only and cannot afford to feed and get much needed vet care for my cats without donations. I spend approximately $500   a month on just food and litter. I have some cats that are in need if serious vet care which  I cannot afford. I also have a number of cats that need to be spayed and neutered. IThe last  thing I want is to bring more kittens in the world! If anyone can help, especially for vet care, I would be truly grateful. Thank you anf God bless you all!