Your units represent a share of the loans, and a loan is two documents. There's the promissory note, which is the borrower's written promise to repay a set amount at a set rate, and there's the mortgage or deed of trust, which pledges the building as security for that promise. The fund owns those. The addresses on the schedule are the collateral behind each loan, not property the fund holds title to.
While everything performs, the fund collects interest and passes most of it through to you as distributions. That's the whole engine. "First in line" means position in the capital stack. A senior or first-lien loan gets repaid before mezzanine debt, and both get repaid before the owner's equity sees a dollar. So if a property that secured a $6 million first-lien loan sells for $7 million, the loan gets paid in full and the equity keeps the rest. If it sells for $5 million, the lender takes the loss the equity can't absorb.
That gap between the loan amount and the property value is the collateral cushion, usually described as loan-to-value. A 65% LTV loan means the property can fall 35% before the lender is underwater on paper. It's the single number worth understanding before any of the rest.
One thing that trips people up later: some of these funds are open-end, meaning you can request redemption on a schedule, and some are closed-end, meaning your money is locked for the fund's life. The documents will say which, and it changes the position entirely.