The ability to be employed and/or compensated for services in the U.S. is dependent upon the non-immigrant visa status held by the foreign national AND the specific immigration regulations which govern the visa.
Many non-immigrant visa categories permit an individual to be employed and/or compensated by a U.S. employer. However, in almost every case, employment and compensation are restricted to an identified, sponsoring employer or organization, for a fixed period of time within a specific capacity.