can you tell me do you pay prior to boarding or day of drop off?

After you have found a sitter and confirmed a booking with them, you will be prompted to pay at that time.

From the Rover Support page (https://support.rover.com/hc/en-us/ar...):

Your card is charged at the time of booking, similar to reserving a flight.

Please note that while your card is debited at the time of booking, Rover holds onto the funds and releases them to the sitter two days after the stay or service is complete.

Commonly asked questions are also answered at https://support.rover.com/hc/en-us?re...