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No. An offer of admission will not be sent until and unless the letter of financial responsibility is submitted. I suggest you check with all the schools to which you applied, as this is a US government requirement, not a USC requirement:
Yes. Do so as soon as possible. If the tiny possibility of being invited for a scholarship interveiw exists for you, you will miss that posibility if the letter is not submitted as soon as possible. The link above leads to the form. Again, I suggest you check with all US schools to which you applied. Your father’s plan to wait until the acceptances are in-hand will not work as those acceptances will not be sent until the letter is submitted.</p>