g10,
I don't have a work permit/green card yet but I don't plan to work forever in America. To study at an Immigration and Naturalisation Service recognised training establishment in the States you'll either be granted a J1 or M1 visa both of which last fo 24 months, I believe. You are not permitted to "work" on either but the M1 allows the holder to gain vocational experience, i.e flying instructor, until the visa expires, then you must return to your place of origin. Or at least this is what I believe to be the case, but I am open to correction
I had looked into getting a green card but the Americans seem to make things deliberately complex. Look at
American Embassy and see if you can fathom it out. I might just give them a call and tell them I don't want to live there permanently, just build up my flying hours so I can get an ATPL then exchange it for one nearer to home.
When do you plan on going over, that is assuming that you do want to go over
Fly safely
BOTR