In answer to your question ..... No, it is not enough
I would suggest $300 for the first rat and $200 for each additional rat (so I would suggest you have at least $900 in a bank account for medical bills), in an account at all times, and replaced as needed
or else a credit card for vet and medical expenses
As you may be aware, female rats need to be spayed if you have access to a good vet that has the knowledge and experience to do it safely. This is not inexpensive but is cost effective in the long run
https://www.ratshackforum.com/threads/why-spay-or-neuter-rats.35402/
In June I rented a car and took a 3 day trip to get some rescue rats spayed and neutered. It went on my credit card as I have little money and will take at least a year or two to pay off. Just so you know how important I believe it is to get rats spayed.
I have a little rescued girl, Clarke, who was 1 year old in August. So far she has had 4 tumour surgeries - so it is not just aging rats who can require expensive vet care ...... and rats of all ages can get resp infections and other illnesses, requiring immediate vet visits and various antibiotics