You can explain your situation and see what they say.
I don't think you're going to find anything free (I looked). There's Affordable Care Animal Hospital at 5858 Spring St. They open at 8 am. If you tell them your situation, perhaps they'll be willing to work something out with you. Most vets are in it because they love animals. Good luck with your baby. One of our babies has an incurable cancer, and I know how stressful it is when they're sick.
Thanks! Your answer is awaiting moderation.