Essentially what are the legal requirements for starting the next Binance, Bittrex etc. When I say in the United States I mean US based customers (preferably registered in the US as well.)
itcoin exchanges, miners, and cryptocurrency-payment processors, operating in the United States are required to comply with federal Anti-Money Laundering (AML) laws.
That means a cryptocurrency user can be prosecuted for violating a number of federal laws. Anybody who converts BTC to USD and sends the money to or from the United States must comply with all AML laws and regulations.
Such laws and regulations are imposed by the U.S. Treasury Department affiliate, FinCEN. The Financial Crimes Enforcement Network is in charge of enforcing the policies and regulations, which serve as a security measure for conducting any financial activity within the U.S. borders.
All money service businesses, including Bitcoin exchanges, come within the provisions of these laws and guarantee a strong bank secrecy, as well as money laundering control. In the case a financial organization fails to abide by the policy, FinCEN is entitled to recourse through competent legal authorities like the FBI or the U.S. Secret Service.
Besides that you will be required to register with SEC.