The first part can certainly be accomplished using HubSpot Payments. Or another option is PayPal payment links which we’ve implemented for a client.
For the second part, it can be partially achieved using multiple form submissions and workflow automation. Since your project also involves sensitive data such as billing details and medical information, you should also check HubSpot Sensitive Data: Sensitive Data Management for CRM | HubSpot
Best regards,
Abraham Ernesto