Once you have sent a settler out and established a town, it will begin funneling some resources back to your capital. Until you upgrade them to towns, the only way to expand them is to purchase new infrastructure with gold. Towns dont require much attention, but you get more benefits such as creating military units and being able to accept more resource bonuses if youre willing to manage multiple cities. The only requirement you need when ready to upgrade towns to cities is decent chunk of gol
