Currently the best way to achieve this is by creating a second
event for the balance payment. You can link the 2
events.
Click here for details.
The system won't automatically check for you, that a person who
purchases a ticket on one event, has made a purchase on the
other. So you would need to check that manually.
We do have a plan to roll out a Staged Payment option for
events. So please check the Updates section on our home page for details on new
features.