Why don't individuals get a Visa when entering a country, as the law requires? Here is a comparison of the minimum wage of normal people in different countries compared to the price of the Visa.

Resources listed in bibliography.

Listed below are different employment visas available for individuals and families.  All of the visas listed allow families to accompany individuals. Usually, however, extended family, helpers (translators, physical therapists, etc.), business partners or domestic help, like nannies and maids, cannot come with individuals, unless they qualify for a visa based on their own reasons.

Temporary Professionals- H-1B visas
These visas only last for a short period of time, and require the sponsorship of your employer. Both the employer and the person applying for the visa must qualify. They typically last for three years, but it is possible to get a three-year extension.

Temporary Agricultural Workers- H-2A visas
These visas are typically seasonal, and require that the farm employer apply for the visa for you.

Temporary Skilled and Unskilled Workers- H-2B visas
Farm workers or high-tech workers do not qualify for this visa. However, it covers a variety of other jobs. The person applying for the visa must have a job offer and the sponsorship of an employer. These visas last for one year, but can be extended to 3 years.

Professional Trainees- H-3
You can qualify for this visa if there is professional training available in the United States that you cannot get at home. This visa has a maximum of 2 years.

Intracompany Transfers- L visas
People qualify for this visa if the company they have been with for more than a year transfers you to the United States. This visa can last for five to seven years.

Representatives of Foreign Media- I Visas
Employees or contracted freelancers for foreign media organizations qualify for this visa.  There are no limits on how many times is can be issued. 

Religious Workers- R Visas
People who have been working with religious organizations for more than two years are eligible for this visa.  They must have a sponsor from a US religious organization.  This issue can last for up to 5 years. 

Athletes, Artists and Entertainers- P Visas
People coming to the United States to join an athletic team or entertainment group are eligible for these visas.

Canadian and Mexican Professionals Under NAFTA Or TN Visas
According to NAFTA, Canadians and Mexicans may conduct business in the United States, if they are in the field of manufacturing, production, sales, distribution, or marketing.

Government Representatives: A, G and Nato Visas
This visa applies to diplomatic or government workers whose services are needed in the United States.

Employment-based Green Cards
People with extraordinary abilities can bypass the temporary work visa and apply for a green card. Depending how vital your job is to the United States will determine your ability to get a green card.

Treaty Traders and Investors: E visas
E visas would apply to those people involved in international commerce. These visas are good for five years but can be renewed.

People studying in the US may qualify for one of the following visas. Students, Trainees, and Exchange Visitors Visas:
Academic Students & Their Immediate Family Members: F Visas
Vocational Students & Their Immediate Family Members: M Visas
Professional Trainees- H-3 Visas
Exchange Visitors- J Visas
International Cultural Exchange Visitors- Q visas

If you are a direct family member of an American citizen or a holder of a green-card, you can qualify for one of these visas below:
Family-based visas:
Fiancés and Spouses of American Citizens, and their children- K Visas
Certain Qualifying Spouses and Children of U.S.
Green Card Holders- V Visa
Family-Based Green Card

People who are suffering treatment that is inhuman and cruel in their country, but not related to just poverty by itself, you can apply for one of the immigration statuses listed below.
Humanitarian Entry:
Victims of Human Trafficking: T Visas
Amnesty
Refugee Status
Asylum

Government Representatives
After you know that you might certify under the rules, you need to teach yourself all of the details of the visa. Some visas let you live in the U.S, but not work in it. On other visas, you have to pledge that you won’t remain in the U.S permanently.
These qualifying circumstances are very important. People who plan to come here as a student, and to later get another visa to stay here permanently, will be denied the student visa as soon as the government finds out. That’s only one of many examples.

Undefined Visas:
These visas had no definitions.
Nurses- H-C Visas

It’s important that people know and understand the rules and guidelines for the visa they are applying for. Keeping current with immigration concerns is crucial. Also, laws, rules, and guidelines change occasionally, so it is important to stay on top of any changes.