I will try my best to help out.
I would recommend an animal hospital (rather than regular vet) and explain the problem and ask questions like "What foods would be healthiest for my cat to eat?" and "What drinks would be healthiest for my cat to drink?" and I would also recommend asking like "can I do a monthly payment such as $91.01 a month for example and if yes what is the cheapest monthly payment I can do?" and if possible and desired do a monthly payment.
I hope your cat gets better.
Good luck and have a great day ; )