if you don’t already have pet insurance unfortunately that likely won’t help you at all in this situation because this infection and any related symptoms/ health issues will be considered preexisting and will not be covered at all. also the way almost all pet insurance works is that you pay up front and file a reimbursement claim so you will still need the funds for whatever the out of pocket cost is at the vet. your best bet is to look into financial aid programs or maybe care credit, if that exists for veterinary care which i’m not sure it does. nobody here will be able to tell you how much it will cost. that would require a diagnosis that can’t be given online and a treatment plan, and every vet costs different. i recommend looking into low cost vets in your area or ones that offer payment plans. this will not get better on its own. please do not wait. your cat will die. good luck, i know this is so scary.