Our Tremere, who is German born, from a covenant in Bohemia, has great ambitions of doing it big in trade. He has set out with a river barge on his way to Riga(Latvia). The Rivers are the traiding highways here, and the barges(bulk-cargo river boats) roam the rivers from Novgorod to Constantinopel. He has decided to try to open relations with the german knights who has taken/are building Riga, and are known as the Sword Knights, and has taken up the cross in the Livonian Crusade under Bishop Albert.

Some of us other magi has tried to inform the Tremere that this trading buisniss is a step in the wrong direction, not to speak of how hazardous it can be to deal with crusaders, and that his studies will suffer from it. But at the same time we gleefully await the profits he will (hopefully)generate. And this way he will be away alot, and not have time to bother the covenfolk with his intrigues and scheeming. He sort of stands out since he is the only magus who isn't from the tribunal, and the rus covenfolk and villagers find him more scary than us other magi, since they don't understand the first thing about him.

But, I am the gm for his expedition to Riga and it is great fun. It is however, one thing I could need some help with:
Rules for trading!!!

Are there anyone out there who have made up some useful rules for trading-buing and selling for a profit in Ars Magica? I don't particularly need rules for the haggling bit, I feel we can roleplay that adecvatly, moderated by some skills, some of which we have developed for this purpose.
But what sort of expenses does a trading expedition generate? How much profit is reasonable? How does the market fluctuate? What sort of deals and organisation did the period traders and trading houses use?
Some of theese questions can be found by reading about the Hanseatic League I imagine, does anyone have any good links to info about them?
Stuff like that is what I'm wondering about. Anyone has any useful advice or information?

~Alex