Buying the mortgage gets you a claim on the building, and the claim has to be turned into title before anyone touches the slab. The usual paths are a negotiated deed in lieu of foreclosure or a foreclosure run all the way to a sale, sometimes with a receiver appointed in the middle so somebody is paying the utility bills. Timing swings hard by state, since some states run non-judicial trustee sales in a matter of months while others require a court action that can stretch past a year, and a borrower bankruptcy stops the clock at any point along the way. Have counsel confirm the process and realistic timeline for the state the building sits in before you accept the memo's schedule.
Your payoff question is a real risk, not a theoretical one. Nothing prevents the borrower from bringing the loan current or refinancing it out at par plus accrued interest and fees. Some note buyers treat that as a perfectly good outcome, a short hold at a strong yield on a 55 cent basis. Others will only buy where the equity is so far underwater that rescue capital is implausible. Which of those two the sponsor is doing tells you what you actually own, so ask them directly and ask what their basis is per square foot of the building if they do take title.
The feasibility work is being done blind, which is the part I'd press on. Without access you're relying on record drawings, the appraisal and any physical needs report in the loan file, and observation from the street. Nobody's coring a slab or opening a riser shaft. Window replacement is the item that most often turns a good basis into a bad one, so find out what they assumed for the curtain wall and whether that number came from anything other than a per-square-foot rule of thumb. Also read the intercreditor agreement if there's mezzanine debt in the stack, because your control rights on the way to title may not be what the summary page implies.
