Separate Application and Registration Fee?

Hello! I have searched extensively but have not found an answer.

Our little school has an application fee on submission of the application form. Once the application is considered, if they are accepted, we then need to collect a registration fee. Our problem is this:

I do not believe we can invoice an accepted applicant until they are enrolled. However, we cannot enroll them until they have paid their registration fee without breaking our admissions flow.

Is our only solution to externally invoice them via Stripe or other solution for this one fee? Our registrar created a registration form separately, but it created a duplicate student on submission. We realized that registration/enrollment information appears to be best handled with the Data Updater instead of a separate form, but then we cannot collect the necessary fee.

Thank you!
Jenn