Bankers and money changers make the life of a traveling merchant possible by exchanging foreign money or holding on to currency for safekeeping and for investment. They might also loan money. Of course, all of these actions are only done at a substantial interest rate. By the Middle Ages, a thin line separated the banker from the usurer, who charges higher rates and might belong to an ethnic or religious minority. The banker’s activity can fuel economic growth, and even kings might be indebted to him.