The Immigration and Nationality Act (INA) is the primary federal law that governs business immigration in the United States. It sets forth the requirements for obtaining visas, green cards, and other forms of immigration status for foreign nationals who wish to work in the U.S.

B-1 visas are for temporary business visitors, not for employment. H-1B visas are for skilled workers, L-1 visas are for intracompany transferees, and E-3 visas are for Australian professionals.

The annual cap on H-1B visas is 65,000, with an additional 20,000 visas available for foreign nationals who have earned a master's degree or higher from a U.S. university.

At least three years of experience in the specialty occupation is not a requirement for obtaining an H-1B visa. However, it is a common requirement for many employers.

The maximum period of stay for an H-1B visa is 6 years, with the possibility of a one-time extension for an additional 3 years.

L-1 visa holders are not eligible to apply for permanent residency. However, they may be able to obtain permanent residency through other means, such as marriage to a U.S. citizen or sponsorship by an employer.

There is no annual cap on L-1 visas. However, there is a limit on the number of L-1 visas that can be issued to nationals of certain countries.

At least two years of experience in the specialty occupation is not a requirement for obtaining an E-3 visa. However, it is a common requirement for many employers.

The maximum period of stay for an E-3 visa is 2 years, with the possibility of multiple extensions for an additional 2 years each.

EB-5 visa holders are not required to maintain a permanent residence in the United States. They may travel freely between the United States and their home country.

The minimum investment required to obtain an EB-5 visa is $1 million. However, a reduced investment of $500,000 is available for investments in certain rural or high-unemployment areas.

A bachelor's degree or equivalent is not a requirement for obtaining an EB-1 visa. However, it is a common requirement for many employers.

EB-1 visa holders are granted indefinite periods of stay in the United States. They may apply for permanent residency after 5 years of residence in the United States.

EB-2 visa holders are not required to maintain a permanent residence in the United States. They may travel freely between the United States and their home country.

The minimum investment required to obtain an EB-5 visa is $1 million. However, a reduced investment of $500,000 is available for investments in certain rural or high-unemployment areas.