There is absolutely NO WAY for F2 to work in any form. F1 can work only under certain circumstances, such as OPT, CPT, economic hardship, etc. And it has to be authorized by either the school or the Department of Homeland Security. So if you want to open a restaurant, you as F1 or F2 cannot WORK there. However, there is no rule against F1 or F2 INVEST in the U.S. The key is 1, you cannot work in the restaurant. That means you cannot receive salary or any other forms of compensation for the time you spend in the business, and 2, you can, however, receive payment from your investment in the business. The payment has to be in the form of, for example, stock dividends.