The basic version of Mobile Passport is free. Depending on your user settings, you may be prompted to provide your account password to download the app from the Apple App Store or Google Play Store, otherwise, there are no fees associated with it. Mobile Passport plus is a premium version of the app, which is available as an in-app upgrade for an annual subscription with a free 7-day trial or a monthly subscription with no free trial.
The stores will charge the price of the purchase in addition to any applicable taxes, depending on your state/country. Both subscription plans automatically renew unless auto-renew is turned off no later than 24 hours before the end of the current period.