J-1 visa is for persons who are approved to participate in exchange visitor programs in the U.S., under provisions of U.S. immigration law. This means that before you can apply at a U.S. Embassy or Consulate for a J visa, you must first apply, meet the requirements, and be accepted for one of the Exchange Visitor Program categories through a designated sponsoring organization. If you are accepted as a participant in an exchange program, the sponsor will provide you with information and documents necessary to apply for the J-1 visa to enter USA.
Students entering the USA on J-1 visa must have valid health insurance for J1 visa that meets certain health insurance requirements for J1 Visa set by the Department of State / visa authorities. For J-1 Visa holders, health insurance is not an option, it's a requirement. If you are applying for a US visa as an exchange visitor, then the first thing you might want to consider before applying for your J-1/Au-Pair visa is health insurance.