For this deal, my mother and I secured financing through a Debt Service Coverage Ratio (DSCR) loan, which allowed us to borrow based on the rental income potential of the property.

A double security deposit can. 

Security Instrument3.

For the security deposits - since we will take over is the seller required to transfer those funds to us?

If you only have 25% equity in the other property and no cash, then that probably will not work as its too risky for the lender unless you also have other properties to secure it with.

I'm actively purchasing multiple properties and would like to leverage hard money loans with terms typically ranging from 1.5 to 2 years.My primary focus is on securing financing that aligns with my investment goals while ensuring that the rates and terms are the most favorable.

I was able to to secure a loan. 

Regarding security with buying the property, I can't say I'm too worried about that.

Plan is so that he can retire and him and my Mom can be financially secure on rental income while my sister and I manage the properties in the trust. 

Most S8 tenants have a history of bad decisions and from all that, many have only learned how to game the system.We embrace S8 applicants, but screen them just like any other applicant.Many have an entitlement mentality and try to leverage their S8 voucher and pretend to be helpless:1) A percentage won't apply because they expect a landlord to waive application fees for them.2) Many cry broke and expect a landlord NOT to charge them a security deposit.3) Many of those same S8 tenants trying to avoid paying a security deposit, won't make an effort to call the list of nonprofits we send them that will pay their security deposit if they apply.4) A lot of them try to avoid paying for utilities.