I have now idea about setting up a provisional file, but something i noticed in the I-864 papers. If your mom carried you on her taxes for that tax year the two of you CAN add your incomes together. From the I-864: "When determining your income, you may include the income generated by individulas related to you by birth, marriage, or adoption who are living in your residence, if they have lived in your residence for the previous 6 months, or who are listed as dependents on your most recent Federal income tax return whether or not they live in your residence."...Then it goes on to say they need to sign a contract between sponsor and household member, the I-864-A.