The immigrant investor can borrow the necessary capital for the EB-5 investment, but it must be tied against personal assets. A loan agreement will need to be shown in order to prove the lawful source of funds.
The investment can be a loan if the lender is not a bank. The lender must show Source of Funds for money they are lending. For example, last 5 years tax returns and other financial documentation indicating where they received $500,000 to loan you.