Gold Coins and Slaves (Fearless Blue)

Hey guys, I've been away from the game for what must be 12 months now, like the new setup.

What is the deal with slave countries though? Just asking before I go off attacking a C3.

When I pay using gold coins to "extend my presidency" am I really paying gold coins to extend my presidency of my empire? Or will I have to dish out 15 gold coins every 30 days for each slave I may take.

Just 30 coins per world, per month Lundy.

Thank you kindly.

Welcome.