In the United States individuals who are not citizens and wish to work usually need a visa. There are work visas, for types of jobs that require sponsorship from an employer. For long term employment, immigrant visas based on skills, education and experience are an option. If you are already, in the U.S. you may qualify to change your status or apply for residency through adjustment of status. Sometimes it is possible to apply on your own without needing a sponsor. Keep in mind that all work authorization comes with conditions and restrictions.