Maintaining friendly relationships with other groups offers a number of advantages. First, the trade agreement and the non-aggression pact that guarantees the security of your country. The Military Access Treaty allows your armies to move freely on the territories of another faction (which, without it, is treated as a violation of borders and deteriorates your relations). This is just another symptom of the larger problem called “Total War Diplomacy,” something that has shown very little love and attention since CA was first born. They even took poor little diplomatic boats and cars on the campaign map. They waved their finger against diplomacy and also took trade routes. Each resource you export brings a sum of money per train. The revenue you receive from the resource can be verified by indicating the resource listed in the Diplomacy with the Mouse tab. To check how much money you get from trading with a group, you have to float on the icon of the trade agreement, next to the group given in the diplomacy tab. In addition, by clicking on a group in the tab on the right, you will see a list of contracts and agreements binding the group, as well as some information about the commercial goods they have (the ones they import and export). Here you can find some personal information about group leaders. At the bottom of the screen are contracts signed by different factions.
If you show with the mouse above the symbol of the given fraction, you will see a list of factors that affect your relationships. There are several possibilities: trade is an exchange of goods that you can produce in certain buildings (wood, iron, exotic animals, etc.). You can act with another group if you don`t have the resource you`re acting on – otherwise they won`t be interested. Different goods have different prices, the more income from trade depends on the amount of resource you produce. On the left (on your side), the interface shows you how much you earn with the trade and resources you export to your trading partner. The right side shows how much money they earn and what resources you import from them. Tilea and Estalia are also very difficult to obtain as business partners for reasons I can`t understand. I have never seen evidence that more commercial resources would increase the likelihood of someone agreeing to a trade agreement. The diplomatic system is very veiled here. I have seen that groups with 200-plus relationships are opposed to profitable trade for them and that groups with 5-strong relationships accept the same trade.