Probably this is a gimmick/rip-off. All employers require you to submit a social security number and you can only get that if you have the right to work here. Not even dirtbag outfits will try to get around this - the stakes are just too high. And, post 9/11, U.S. immigration officials take a VERY dim view of being in the U.S. illegally. If you get nabbed you could get deported and banned from ever getting a U.S. visa ever again.
Marry an American girl (if you can stomach one) and then go to Juneau or Ketchikan around February and start pounding on doors. 500 on floats is often bandied about as a minimum. Also try the fishing lodges - rumor is they hire guys with much less. Look on the web. Expect dismal pay - $130/day is one number I've heard - and a short season Jun, Jul, Aug.
Hope this helps.