Trade has two Layers: One is being State-Controlled the other being Merchant/Trade Company/Merch Republic controlled.
Trade Routes and InfrastructureTrade Routes and Infrastructure belong to the First Layer. Two Governments need to strike a Trade Agreement to allow Trade to be happening between their Countries
legally.
Once that is done the proper Infrastructure needs to be built to allow for Trade Ships to anchor and Caravans to reach the City.
Infrastructure is divided into Land and Sea. With the owning Government needing to build and maintain them to allow Trade Caravans and Trade Ships to collect their Cargo.
LandTrails - free - 1 Caravan Capacity - Trails are barely more than ways which came to be via massed travel over the same ground. They start to appear once a Trade Agreement has been met.
Dirt Roads -3 Ducats Cost - 0,5 Ducats Maint - 3 Caravan Capacity - Dirt Roads are the result of cultivating the wild nature around a Trail. Removing the Weeds, cutting down bushes and Trees in the way and elevate the whole thing a bit with a filling of Earth. Though far better than Trails a simple rain can cause it to become a muddy swamp making Travel almost impossible.
Paved Roads -5 Ducats Cost - 1 Ducat Main. - 5 Caravan Capacity - Paved Roads are paved with Stone further cultivated and regularly repaired and cleaned by either Local Garrisons or Hired Workers. It takes Floods and landslides to make travel on these impossible
Post Roads and Stations - 10 Ducats Cost - 2 Ducats Main. - 10 Caravan Capacity - An Intricate and well maintained Road System connects the Two Cities. On the Way are Post Stations which check your papers and provide shelter for government Officials. If you have the right papers swift and secure Travel is assured and not even the worst of natural Disasters and only the most Daring and well equipped Bandits Armies are able to disrupt Trade on such a Road.
Imperial Roads, Towers and Post Stations -15 Ducats Cost - 5 Ducats Main. - 20 Caravan Capacity - Highly Maintained Well patrolled Highways with intricate arterial roads, every few Miles on encounters an Outpost with a Tower, a small garrison a post station, barracks, a tavern and a extra buildings for government officials. Entire villages grow aroudn these places. the Roads are Secure against any Disaster and such a System provides a Defensive Factor all of itself.
SeaFishing Port- Free - 1 Trade Ship - its actually just a single badly maintained jetty on which small fishing boats dock. a Trading Ship has to wait in deeper waters and unload its cargo with the help of smaller boats able to dock at the jetty.
Harbour- 3 Ducats Cost - 3 Trade Ships - a proper Harbour allowing ships to actually Dock and unload their goods directly quickly speeds up the Trading Process. An attached inn allows men to stay over night comfortably.
Trade Port - 5 Ducats Cost - 5 Trade Ships - Adding to the Harbour some Warehouses more Jetties to dock, a proper Customs House, some inns and cathouses.
Merchant Quarters - 10 Ducats Cost - 10 Trade Ships - Adds an extra Quarter for International Merchants into the City. There Trade Companies can build Warehouses, Barracks and Headquarters for their Companies.
International Trade Port- 15 Ducats Cost -20 Trade Ships- a bustling Metropolis, a city within a city. Dozens of Warehouses a massive Customs House with dozens of officers a garrison alone to patrol the Port, Inns, Taverns and entire red-light districts catering only to the needs of lonely seamen. It is is to get lost in the vast Districts of such a Trade Port.
Trade Posts, Caravans and Trade ShipsBelonging to the second layer, once Trade becomes viable Merchants and Trade Companies can begin to construct Trade Posts in Cities to be able to Trade. A word of warning though, each City, Town or Village has only Space for one Trade Post, usually that is. At a certain size of its trade facilities and population a City might have space for more than one Trade Company.
A Caravan/Trade Ship costs 0,5 Ducats and once bought has no upkeep. It transport Two Ducats worth of Goods each season.
Trade PostsSo finally you bought a Caravan, the Trade Agreement of your Country with the other one is struck and a Road connects the two. But wait we are not finished yet! To be able to trade at all you need a Trade Post.
Trade Post - 1 Ducat - Produces 1 Good per Season - Company Cap 1 - a Simple Warehouse with some outlying rooms and a few guards to protect it.
Merchant Enclave- 2 Ducats - Adds +2 Goods per Season, City Population Grows by One - As your interest in Trade grows mroe and more Merchants are settling down in the City to do their everyday business
Guard Quarters- 2 Ducats - +2 Company Cap - Adding a wall around your Quarter of the town and employing a bunch of Mercenaries who keep watch that nobody steals something out of your Quarter.
Local Branch Offices - 5 Ducats- +1 Company Cap - +1 Goods Per Season, City Pop grows by One - Sometimes land trade becomes complicated. If you have to travel through three or four Countries paying tolls at each and everyone of them you dont make any winnings, you only lose money. Thus Opening Branch Offices which take care of monetary and trade matters and make sure that the money reaches you via ways which aren't taxed and tolled are a real blessing.
Docks - 2 Ducats - +1 Ship Cap - Allows you to construct more Warships.
Company HeadquartersAll that money and those Trade Goods have to go somewhere and that is usually the Company Headquarters.
Great Mansion- 10 Ducats - +3 Company Cap - +3 Ship Cap - +1 Regiment Cap - Population Grows by 1 - By adding various more Offices, Warehouses a few more Jetty's and an entire armory and new barracks the usual Mansion a Trading Company owns becomes a veritable City within the City
Palace - Requires Grand Mansion - 20 Ducats - +5 Company Cap - +5 Ship Cap - +2 Regiments Cap - 1000 Coursers - Goods Produce +2 Ducats - Population Grows by 2 - a Pompous Building with its own Stables, its very own Harbour, Vaults, Warehouses and more rooms than one cares to count is something only the richest can afford.
Grand Palace - Requires Palace - 40 Ducats - +10 Company Cap - +10 Ship Cap - +3 Regiments Cap - 2000 Coursers, 1000 Destriers - Goods Produce +2 Ducats -Population Grows by 2 - Dwarfing even the dreams of even the richest Feudal lords this Merchant Company has the Power to level kingdoms with the mere threat of an embargo
more upgrades to the Palaces may become available with more advanced Technology. Or if i have some more ideas
ConcessionsApart from Normal Trade there is also Trade with Strategical or Luxury Resources. Since these Rescources are quite valuable (for example Prize-Horses, High Grade Timber, Iron, Weapons etc.) two States need to agree to trade such resources with each other. Once an agreement has been met the resources need to be actually traded, at which point Trade Companies come into play.
Once given such a Concession a Trade Company gets an Convoy which needs to move instead from a Trade Post to the Company Headquarters or Branch Offices, between two Countries.
Each Convoy provides Four Ducats for a Trade Company but has to be guarded specifically by at least one Company of Soldiers.
Tolls and TariffsOf course the State wants a bit of the cake too, thats why he can raise tolls for using his roads, tariffs for using his ports and on top tax you on your winnings. On the other hand if the state gets to expensive for you, you might consider moving.
Moving your Headquarter is free but takes a whole season and you won't earn anything during it.