If I understand your question correctly:

A merchant arrives on amber on turn one. You hear him say "establishing trade," or something like that. You hit the next turn button. You get the florins from trading amber.

The next turn, you move him from amber to furs. You hear the "establishing trade" or "money to be made here" comment. You hit the next turn button. You get the money from furs.

However, if it takes you longer to get from amber to furs in one turn, you do not get the income from amber while travelling to furs, if I understand correctly.