Yep, you have to file it. It would count as income from a business, just like if you had set up a hot-dog stand on the street corner. In the US, you'll want to add a schedule C to your 1040, which is really easy if you use a program like turbotax.
Say I am only studying in USA at university then going back to another country, do i still pay to USA?
also if i dont have a residence to any country who would i pay to?
Say I am only studying in USA at university then going back to another country, do i still pay to USA?
also if i dont have a residence to any country who would i pay to?
You don't have a residence to any country? Are you in a country on a working visa or something?