On the TurboSBIR landing page first select the Pricing tab.

On the Pricing page you will be prompted to customize your payment model depending on the needs of you and your startup. If you are looking to just submit a single proposal, select the Single Proposal option.

You will then be prompted to select your payment option. You can choose to select an upfront payment plan which is a single flat fee or a contingency model which means only in the case that you are awarded a grant will you be charged a percentage of that grant.