Making extra money for Dungeons & Dragons parties, first revision

Dungeons and Dragons needs rules for our player characters (PCs) to earn extra money by going beyond ways described in modules, such as The Keep on the Borderlands.  Our PCs can be high fantasy adventuring against non-player characters and monsters one day.  The next day, our PCs could earn coin while working to gain additional money from more mundane activities.

 

For example, they could collect food by harvesting wild fruit, while hunting deer and game birds such as wild turkeys for wealthy individuals of the keep.  What about hunting for fur-bearing animals?  The player characters could establish a fur trading company, over time becoming wealthy like John Jacob Astor’s family became wealthy in the real world.  Players can learn how to build a fortune studying how Mr. Astor created his wealth.

 

They could fish for game fish like Trout in the nearby river.  Are the trees around the caves usable for lumber?  The trees could be hauled to the river, chained into large rafts, and then floated down the river to markets.

 

The module The Keep on the Borderlands describes a wide river near the keep.  So, why is this river not being used to move people and cargo, soldiers and their equipment?  The players could rent or own a riverboat that they use as their home as they travel the world.

 

Is the rock, which the caves are within, usable for building structures?  Turn the caves into a surface rock quarry and in a few years the caves will be eaten up by the quarry.  To become wealthy selling stone, along with metals such as iron and silver.  Other valuable products that could make the PCs wealthy are coal and salt.  Forever destroying the Caves of Chaos is something that my player characters can dig.

 

Also, our PCs could find caves filled with magical crystals used for creating magical artifacts.  Those caves would be based on the real world Cave of the Crystals or Giant Crystal Cave that is a cave connected to the Naica Mine at a depth of 300 meters, in Naica, Chihuahua, Mexico.  Such crystals could be worth tens of thousands of gold coins each.