Income
From Hyborian War Wiki
Your kingdom may receive a small income each turn from any or all of the following (depending on your actions and their success):
1. Each troop successfully raiding a foreign province. 2. Wealth brought back by adventuring heroes. 3. Tariffs on foreign trade routes that run through provinces under your control.
Your kingdom may receive a large portion of income from:
1. Tax revenue from each province under your control. 2. Trade revenue from routes established with kingdoms abroad.