From what I understand you can now do it on line. With respect to stable economies the rates of exchange do not change that often. So if you do find a combination with a decent spread ...you can do it daily for as long as the opportunity lasts. How much you make depends on how much currency you are trying to exchange initially. When I was doing it years ago I was working with a small amount of money, but was picking up a few extra bucks every week. The more you put at risk...the more you make on the spread.

I have read right now that an interesting development is occurring with the relationships among U.S. dollars, Euros, Australian dollars, New Zealand dollars, Canadian dollars  and British pounds.