Please see this page for more information about fees.
If you want to see if your card carries a fee, you can do so by going into your Settings > Banks & Cards, and tapping on the card. You'll also be notified while adding a card that falls under this category.
Some credit card providers charge cash advance fees (possibly including an additional dollar amount or percent rate, in addition to other possible cash advance service fees, including a higher APR) if you use your credit card to make payments to friends on Venmo. For more information about whether your card provider charges these fees, contact your card provider.