Is it possible to use securities as a collateral?

A margin account allows 50% to be taken out of the account. Or 70% might be allowed for the purchase of real estate. Institutional margin rates can be found. Otherwise the assets just improve loan qualification and loan qualification is still needed.

The $100k on margin, at 50% margin, is without loan qualification and without a lien on the real estate. The $140k on margin, at 70% margin, might be putting a lien on the real estate but there is probably not much loan qualification.

Well, in standard brokerage accounts, "portfolio margin" is available with large account balances. Then "portfolio margin" can go up to very high margin percentages but "portfolio margin" is based on liquid positions held entirely in the account. To take value on margin out of a brokerage account, for the purpose of buying real-estate, then the 70% margin level is about the best deal that can be found. To take value on margin out of a brokerage account, just for general use, then the situation is back to the standard 50% margin level.

Equities may be used as collateral for a loan. In the US this is sometimes referred to as Securities Based Lending.

Example #1 - Merrill: https://www.ml.com/solutions/structured-lending.html

Example #2 - Wells Fargo: https://www.wellsfargoadvisors.com/why-wells-fargo/products-services/lending/securities-based.htm

If you are buying a house, keep in mind that typically that subject property would be the collateral, not your other assets. You could if you want get a lower rate through balance transfer pricing where you move your assets to the lender's broker (e.g., Merrill for Bank of America, Wells Fargo Advisors for Wells Fargo) to get 25-75 bps off the rate. Your stocks could also be used as assets for qualifying purposes for the home loan (when requiring a certain amount of cash to close or a number of months of reserves). This is assuming we're talking about residential home loans here. This could be combined: move assets to get the better pricing for the home loan, then use the assets for Securities Based Lending to help fund your EB-5 strategy.