You haggle and try to strike a good deal with the monks. You may not make as much money as you would have done if you'd hired a boat yourself. But then at least you don't have to worry about pirates.
Why give up your rights as a burgess in a royal burgh? Use the fact that the king has granted you permission to travel abroad and sail overseas to make a profit.
Which card will you play?
Actually being a monk seems rather an attractive idea. Why not give it a go?