You don't say if you currently own a home or not in the US.If you do, the easiest way to finance a purchase like this would be to borrow against the equity you have built in your own home in the US.  

Borrow against one property every year on a 15 year note and put them all under property management, or borrow against all 15 all at once.

The seller doesn't have the borrower's driver license or any identity verification paperwork.

More about have you already pruned your assets to free up money or borrowing capabilities. 

Is it possible or worthwhile to put a few properties into a trust (of some kind...) for the purpose of making it easier to borrow against equity?

We do have access to a HELOC on the property which we leveraged to purchase our current primary residence (balance borrowed has been fully repaid at this point) but we would rather not pull that lever to roll into a new property given current interest rates and the adjustable nature of the HELOC. 

Borrowing money to use as a down payment so you can borrow money is a recipe for disaster.

Then you spot “Vinnie’s Beer, Pizza and VCR repair” is paying a 50% interest rate on the money it borrows.  

So you’ll need another huge mortgage if you borrowed a lot to buy the building.  

@Daniel BryanI agree with JacobBetter returns elsewhere and downside is if your borrower defaults depending on the state it could take years to foreclose and run all that legal and holding costs which wipe out any gains.