Unet Vehicle permission problem

My intention is to build a vehicle that any given player can pilot can drive if the seat is available. I have already managed the player's command to drive a vehicle owned by the server, but I am failing to code the "asking for permission to enter" part.

Below is my general ideal of that operation:

1)Player interacts with vehicle locally and ask the server whether the seat is free

2) Vehicle(server-side) figures out if the seat is available and tells the player that started the interaction if it's ok. Vehicle then update it's status.

3) Player(client-side) receives the answer, enters vehicle and allow drive commands (which I figured it out already).

Here is a diagram to help ilustrate it