When getting braces, do you have to pay in full before they put them on or do they still put them on your teeth with payments?

Hi.  In our practice, individual treatment plans are developed by Dr. Schudy via exam, x-rays, and molds, are priced accordingly:  Invisalign requires a 33% downpayment on the total price, and Braces require a 25 % downpayment.   Both treatments' remaining balance is divided evenly for the following 20 months.   Patients usually schedule one appointment per month and a payment is made with our receptionist following the appointment as well as scheduling the next month appointment.