The Gold Mine produces coins, the currency listed in building upgrade costs. Its name refers to the mine, while its production stat is Coin Output/hr. The first plot requires Base level 8.
How coin production works
At level 1, a Gold Mine produces 720 coins per hour. It produces 7,200 at level 10, 14,400 at level 20 and 21,600 at level 30. Higher levels change the recurring output; they do not grant that amount as an immediate upgrade reward.
Coins from base production need to be collected. Production has a capacity, and the game can notify you when it is full. The mine's hourly rate and the coins already waiting to be collected are different quantities.
What the Coin Vault does
The Coin Vault raises protected coin quantity. It is not another coin producer. The mine supplies coins, while the vault changes how much is protected.
Food and iron come from their own buildings. Their availability does not replace a coin requirement when starting construction or an upgrade.
