Business and Tourism(B1/B2)
Generally, a citizen of a foreign country wishing to enter the United States must first obtain a visa, either a non-immigrant visa for temporary stay, or an immigrant visa for permanent residence. The "visitor" visa is a nonimmigrant visa for people desiring to enter the US temporarily for business (B-1) or for pleasure or medical treatment (B-2). People planning to travel to the U.S. for different purposes, such as students, temporary workers, crewmembers, journalists, etc, must apply for a different visa in the appropriate category.
Under U.S. immigration law, certain work can be done using the ordinary tourist/business (B-1/2) visa. This includes attending business meetings, purchasing property, negotiating and signing contracts, gathering and filling orders, completing market surveys, attending conferences or short training courses and buying equipment, etc.
For the "back-packer," there is no provision in U.S. immigration law for the "working holiday" visa, popular among tourists traveling to Canada or the U.K. If visitors contemplate working casually during an extended excursion "walking about" the United States, doing so would violate the terms of the tourist visa (B-1/2).
Prohibited work includes working for family or friends as a live-in baby sitter and any casual job that earns an income from U.S. sources. For certain seasonal work such as at ski resorts and summer camps or as au pairs, there are some opportunities under the exchange visitor visa (J-1) program.
Note: In order to be granted a non-immigrant visa, you need to overcome the presumption in Section 214 (b) of the Immigration and Nationality Act (INA) that all visa applicants are intending immigrants. You may overcome this presumption by providing evidence that you have strong, binding ties to your home country and that you have no intention of abandoning that residence. There is not a standard set of documents required to overcome this presumption.
U.S. Customs and Border Protection
Anyone who applies for a visa must understand that holding a visa does not guarantee entrance into the United States. Although you were issued a visa, only U.S. Customs and Border Protection (CBP) have the authority to allow you into the U.S. and to determine the length of your visit. At the port of entry, a CBP official must validate your Record of Arrival - Departure (Form I-94) which tells you how long you may stay. If you want to extend your visit, you must file an Application to Extend Status (Form 1-539) with United States Citizenship and Immigration Services (USCIS). The decision to grant or deny the extension rests solely with USCIS. Consular personnel can answer questions only about visa applications and qualifications.