Within the realm of employment-based green cards to the United States, the so-called second preference category is designed for the following types of people:
To qualify in the second subcategory of EB-2 visas, you must be coming to the U.S. specifically to work full-time in your field of expertise. With limited exceptions, you must have a definite, permanent job offer from a U.S. employer. Self-employment will not work for this category.
Labor certifications – a long and complex certification of the unavailability of U.S. workers discussed in Timeline of the U.S. Labor Certification Process -- are technically required for this category. However, you can potentially avoid the need for labor certification by using the exception for national interest waiver cases, discussed below.
The exceptional ability subcategory of the employment second preference covers people in the sciences, arts, and business. It’s easily confused with the employment first preference priority worker subcategory for persons of extraordinary ability, discussed in this article on EB‑1 Visa Eligibility for Priority Workers. However, the requirements are slightly less narrow (though people with jobs in education and athletics are left out of this second preference subcategory).
Typical eligible workers might include economists, lawyers, doctors, veterinarians, physicists, market research analysts, geographers, mental health workers, and marriage and family therapists.
The main benefit of this subcategory is that you don’t need to have received international acclaim in your field. Proven sustained national acclaim will meet the required standard. You must, however, still be considered significantly more accomplished than the average person in your profession.
Your spouse and your unmarried children under the age of 21 may also be eligible for green cards as accompanying relatives.
If you can show that your presence will benefit the U.S. in the future, you may be able to apply without having a job offer or labor certification, through what’s called a national interest waiver. In order to “benefit” the U.S., you’ll have to show that your work in the U.S. will have a favorable impact on its economic, employment, educational, housing, environmental, or cultural situation, or on some other important aspect of U.S. life. The impact must be national in scope -- in other words, a public health researcher at a federal agency or a university would probably pass, while the same person coming to provide services at a local clinic would probably not.
You’ll also have to show that the field in which you’ll be working has “substantial intrinsic merit”—in other words, that it’s a good thing in and of itself. In addition, you’ll need to demonstrate that you will prospectively benefit the national interest to a substantially greater degree than a similarly qualified, available U.S. worker would. (Unfortunately, USCIS often reinterprets this requirement to mean that you must show that forcing you to go through the labor certification process would actually have an adverse impact on the U.S. national interest. A local labor shortage is not considered to be an adverse impact.)
Because the combination of the above criteria is difficult to satisfy, obtaining a national interest waiver is harder than you might expect, and you will definitely need a lawyer’s help.