To enable automatic buying and selling in a trading office, you must hire a Manager (also known as an administrator). Though managers are quite expensive, they are worth it as automation allows for much larger trading volumes at better prices, requiring minimal intervention.
Setup for buying
You can adjust the stock amount and purchase price of goods. You can also Lock Minimum Store Quantity to prevent goods from being picked up by an auto-trade ship.
The picture below illustrates the possible settings for buying goods:
With the Buy Beer stock at 0, the Manager will not buy any Beer from the town.
If the Buy Bricks stock is at 20, the Manager will always try to keep at least 20 Bricks in the office. As soon as there are less than 20, he will attempt to purchase the remaining amount, at price of 79 gold pieces or less. He will not buy more than that amount.
Setting Buy Cloth stock to 20 and locking Min. Store Quantity will ensure that 20 Cloth or less will always be kept in the office, and no ship will be able to take it out if there is 20 or less Cloth left.
Setting Fish stock to 20 (note that there is no Buy option selected this time) and locking Min.Store quantity, will ensure that Manager will keep 20 or less Fish from being picked up by auto-trade ships, but he will not buy or sell any Fish.
If the Buy Grain stock is set to 9999 (the maximum possible amount), the Manager is forced to buy all grain at 110 gold pieces or less, until there are 9999 loads in stock. This is the maximum amount that the game can deal with.
The main disadvantage of the manager is that there is no option to purchase one amount while keeping a different amount locked.
Setup for Selling
You can adjust the stock amount and sale price of goods. You can also use Lock Minimum Store Quantity to prevent goods from being picked up by an auto-trade ship.
The picture below illustratess the possible settings for selling goods:
If Sell Beer is set at 0, the Manager will sell all Beer until the price drops below 42 gold pieces.
With the Sell Bricks stock at 20, the Manager will always try to keep at most 20 Bricks at the office. As soon as there are more than 20, he will attempt to sell the excess amount, until the price drops below 90 gold pieces.
Setting Sell Cloth stock to 20, and locking Min. Store quantity will ensure that at least 20 Cloth will remain unsold, and no ship will be able to take it out of the office if there is 20 or less Cloth left.
Setting Fish stock to 20 (note that there is no Buy option selected this time) and locking Min. Store quantity, will ensure that Manager will keep 20 or less Fish from being picked up by auto-trade ships, but he will not buy or sell any Fish.
Setting Sell Grain stock to 9999 (which is the maximum possible amount) will prevent the Manager from selling any grain, unless there are more than 9999 loads in stock. This is the maximum amount that the game can deal with.
The main disadvantage of the manager is that there is no option to sell one amount while keeping a different amount locked.
Lock Minimum Store Quantity
This option prevents a captain from picking up raw materials that are being used by businesses in the town.
The main advantage is that production is not halted.
A better example is with timber, the game's most important raw material. If timber stocks are depleted, the production of any meat/leather, beer, iron goods, salt, pottery and bricks will be halted. Note that you will need to adjust minimum stock levels as production increases.
For example, you may be selling necessary timber in Luebeck to supply winter demands, but your industry is consuming more per day than the amount you have withheld from sale. Your workshops will underproduce leaving you with fewer goods to sell. So, increase the withholding level to over one day's industrial consumption.
Comparison with Captains
Managers are similar to Captains on auto-trade, in that they may perform buy or sell operations by themselves. Some people prefer to park a stationary ship with a captain in a city to perform administrator's duties, without having to place a trading office. However, later in the game this can be inefficient. Below is a list of similarities and differences:
Both have a skill level that improves over time (from Stage 0 to Stage 5)
Both buy goods at a discount according to their respective skill level. A Manager can get up to 8% discount (at Stage 5), while a Captain can get up to 10% (at Trade 5). These bonuses are not applied when selling goods.
The Manager buys goods once a day, the captain twice.
Managers can use the Lock Minimum Store Quantity feature to prevent an auto-trading ship in the town from taking away essential raw materials.
The Manager's interface settings are more limited.
Managers don't spam annoying "Ship Trade" messages twice a day (Workaround: You can stop these by adding an empty town at the very top of your list)
Stages and Cost
Managers have a skill level that provides a small bonus when they purchase goods, but does not affect sales. This skill level improves as the manager gains experience, based on the volume of trading he does. You will be notified whenever this happens.
This skill level ranges from Stage 0 to Stage 5. At Stage 5, the manager grants an 8% discount on purchases. The daily wage of a manager depends on his Stage. Additionally, every production facility and warehouse in the town increases his daily wage by 1 gp.