We don't have any money set aside, just keep some freed up in case. Our vet lets us make payments to him whenever the bill gets out of hand. If you can always spare $2-300 a month to make vet payments you should be good. Our bill has never gone over $7-800 for a visit, that's with no major illness or injury. Check with the vet you plan to use and see what their policy is on payment. Some want everything paid in full at the time of service. That of course would be a different financial plan.
"Until one has loved an animal, part of one's soul remains unawakened..."
- Anatole France