ok, but you need some kind of visa right? can you be a foreigner living in a foreign country? i know foreigners working for a bank being licensed, but in a case of an independent trader not physically present in the us?
Series 7 is not a form of work permit, you can live abroad and not be a US citizen or resident alien and have series 7.
Go to this site http://www.prometric.com/FINRA/default.htm and it will tell you the international locations where you can take the Series 7. Please note not every country has a testing center for the S7 so you may have to travel to another country. The UK eg has several testing centers while smaller countries have none. Hope that helps