If you have a user that does not need to be billed but still needs to schedule time in the kitchen, the easiest solution is to set them to Manual payment processing and assign them a custom hourly rate of $0.
When you approve them as a client from your Prospects tab, you will be prompted to select their billing plan. Before you approve them, you can set them to Manual payments (this will make it so they aren’t required to upload a payment method). From here you can set this client to Hourly, then upon approval, assign a custom hourly rate of $0. This can be done in their client settings under the General Tab (Clients > select client > General > Edit Billing Plan > Custom Hourly Rate). Once they have been approved as a client, they can start booking time in the kitchen.