Unfortunately, there is no professional rugby in North America. The highest level of play is the semi-professional "SuperLeague". Which is not to say that there are no American professionals. A number of the USA Eagles do make their living playing the game, but do so with foreign clubs, generally English or French ones. The way one achieves this is to join your local club, learn the game and the physical skills it requires, and then do the best you can. If you've got what it takes, you'll work your way up through the American system and the USA Eagles, and ultimately be scouted by a professional side. They do keep an eye on the top level North American clubs. The other alternative is to attend a college with a strong rugby program (U.C. Berkeley, Brigham Young and U. Penn are good examples), where you might also catch the eye of a European scout. Good luck.