Your day-to-day expenses in the U.S. (housing, food, transportation, etc.) must be completely covered by your salary/stipend and/or your own personal funds.
The American authorities require that you dispose of funds equivalent to State minimum wage.
If your internship is unpaid or paid less than minimum wage, you will be asked to either provide a bank statement or a guarantor letter.
We recommend that you pay careful attention to the way you will finance your stay keeping in mind that any other job aside from your internship is prohibited and that, in some cases, you will receive your first wages only at the end of the first two weeks of your internship.