Employment-based Nonimmigrant Visa

There is no limit on the number of renewals.

Professionals of Canada or Mexico
may work in the US if (1) they are. citizens of Canada or Mexico; (2) their

profession is on the NAFTA list;
(3) they are to work for a US employer (self employment is not permitted);
and (4) they have the qualifications of the profession

Citizens of Canada and Mexico may work in the United States up to a period of one year in one of several specifically designated professional positions in TN status.