Treat the withholding tax and the eventual income-tax liability as a cost of raising the capital, separate from the EB-5 threshold, the regional-center administrative fee and the USCIS fees under the fee schedule. The adviser's net-cash schedule should show all of them.
Raising the capital has its own price
Hypothetical example: a Rothesay executive plans to withdraw exactly the EB-5 threshold from his RRSP and is surprised that the amount arriving in his account is far smaller. RRSP withdrawals are subject to withholding at source and are taxable income, and a commuted pension value may have a taxable cash portion. The capital budget must therefore start from the gross withdrawal needed to produce the required net amount, and that gross figure, with its tax, is a cost of the plan.
On top of that sit the regional center's administrative fee, which is not part of the qualifying investment and whose refundability depends on the offering and subscription documents, the Form I-526E and later Form I-829 fees set by Form G-1055, immigrant-visa processing fees, medical examinations and professional fees for source-of-funds preparation. Cross-border tax advice on the timing of withdrawals relative to a change in tax residence is a separate professional question that can change the numbers significantly.