The full minimum amount of the investment must be made at the time the I-526 is filed. However, you do not have to spend the full amount at the time it is filed.
USCIS regulations requires that the I-526 petition is accompanied by evidence that the required amount of capital has been placed at risk, and notes the following:
"Evidence of a mere intent to invest, or prospective investment arrangements entailing no present commitment, will not suffice to show that the petitioner is actively in the process of investing. The alien must show actual commitment of the required amount of capital."
The capital does not have to be fully invested at the time of the filing of the I-526 petition. However, the evidence provided in support of the investor’s I-829 petition must show that the investor has invested or was actively in the process of investing the capital, and that the investment was sustained throughout the period of conditional permanent residence.