If the game will take place in the 15th century on the territory of the Czech Kingdom and the country will be on the brink of civil war, one of the very profitable way to earn some cash should be smuggling. On the Czech kingdom, rulled by Hussite, embargo was imposed by the Pope. This, of course, very well used buyers from Silesia and Moravia (though these countries were Catholic). Polish smugglers also not idle.
PS: Who would be interested in about this time, and the Czech countries at this time, to know more, I recommend books by A. Sapkowski, Narretrum (the whole trilogy is great). They are in it, although elements of fantasy (magic, supernatural beings, etc.), but in its description of the life of “ordinary” people, this book is great