Is it possible to prevent submission until the payment is made?

Two, we are looking to potentially use this service to accept payment too. There was a question about making sure that the submissions aren't entered until payment is made, so I wanted to confirm that that is indeed the case.

You will not receive a submission until the payment is made.

Which payment integration will you be using? 

Mastering Payment Form Integrations with JotForm 

The forms with a payment integration that have credit card fields, like Stripe, PayPal Pro, Autorize.Net, cannot be submitted if the incorrect credit card details are entered. 

If you will be using PayPal Standard, you users will be redirected to the PayPal checkout page once they submit the form. If they make a payment they will be redirected to the Thank You page and you will receive a submission. If they abandon the payment their submission will be marked as Incomplete payment. 

How to View Incomplete Payments