In Total War: Three Kingdoms, having a healthy Treasury is vital to success. Armies, settlement upkeep, and building up your empire will all cost money. To ensure success, you want to maximize the profits that you can make from each settlement you own.
The first thing to understand is that there are three different types of income you can make from a settlement. Peasantry, Commerce, and Industry all provide different amounts of money, directly affected by the types of buildings in each settlement.
Some buildings will provide inherent bonuses to income. For example, an Inn will provide a bonus to any income earned through Commerce. If you have a settlement that is already providing a lot of income from Commerce, building an Inn is a good idea because it will increase ALL income from Commerce, not just the income it generates itself.
The Benefits of Profits Administrators
Every turn, each building will produce a certain amount of income, and this can be affected by using profit administrators. To appoint an Administrator, simply click on the Administrator button just above the Assignments button for your Commandery. It will be the third small, circular icon. After you click on it, a menu of all the characters you can appoint as administrators will appear.
If you scroll over each character, you will be able to see the bonuses that they will provide that Commandery. What you want to do is pick a character that matches up well with the different types of things produced in that Commandery, and provides the best bonuses to the types of income you earn from it.
Some characters will offer vast bonuses to a certain type of income, while others will provide small bonuses, but to a broader range of income sources.
By making sure you assign the right administrator and then updating them as the things produced within the Commandery change, you can ensure you are earning as much money as possible to help further your empire.