How can a real estate credit line be used as EB-5 source of funds?

As long as you actually own the property you are borrowing against, this should be an acceptable source. You will also need to show how you purchased the property initially.

It can all come from the credit line, but you have to show how you earned the money to purchase the home.

A secured credit line is no different than a mortgage. As long as the credit line is secured by the property in your name and the bank is willing to give you the funds, it could be the full investment amount. I would assume that the property is worth at least a couple of million if the bank is willing to provide you with the full $500,000 minimum required. What USCIS will look at is whether the transaction is within the purview of normal financial transactions if you are doing things that are too creative and not seen in the United States, you may invite more scrutiny.

You may obtain a mortgage loan or home equity loan using your property as collateral, and use the entire amount for your EB-5 investment. The appraised value of the property should be equal to or greater than the loan amount.

You can used borrowed funds (credit line) for an EB-5 investment as long as the loan is secured against personal property that is worth more than the amount of the loan. You should make sure your appraisal can stand up to scrutiny also. The full investment amount can be financed with a secured loan.