The Event Pay Later option now allows you to have your event guest choose to pay at a later time for their purchases. This is a setting that you need to turn on while setting up your event. While editing your event navigate to the "Event Settings" tab, at the bottom of that page you will find a setting called, "Allow Purchaser To Pay Later". To turn this option on click on the toggle button next to the title.

This feature will add a checkbox to the Event Form that the purchaser can check to Pay Later. The cost of the purchase will then be added as a balance for the purchaser to pay at a later date.