Though I don't think NOI in residential has any practical use in valuations or towards other financial instrument applications, it definitely is helpful to analyze synergies forecast in OPEX when you get multiple properties. 

"For purposes of enforcing the due-on-sale (or due-on-transfer) provision, if any, in the security instrument, theservicer must consider all of the following situations to be a transfer of ownership:- the purchase of a property “subject to” the mortgage loan,- the assumption of the mortgage loan debt by the property purchaser,- any exchange of possession of property under a land sales contract or any other land trust device, and- in cases in which an inter vivos revocable trust is the borrower, any transfer of a beneficial interest in thetrust."

Our friend and real estate agent, instrumental in this acquisition, recommends a family interested in a month-to-month rental of the vacant unit, beginning shortly after closing.

I view a HELOC as a great short term debt instrument to get you into deals - like a flip, BRRRR, or a deal that you can't pass up while waiting to sell another property. 

There is/are often a new instrument(s) (quitclaim deed, confirmatory deed, easement, etc.) executed and recorded.

You should do a google search for 'instrument of service,' which, I would assume is what you got from the architect.

cloa...Note should include a provision similar to the following:FOR VALUE RECEIVED, I, [Borrower name] (hereinafter known as “Borrower”), promise to pay to the order of [Trustee/trust, payment address] (hereinafter known as “Lender”) the sum of Fifty-Two Thousand and 00/100 Dollars ($52,000.00), with interest from the date hereof until paid at the rate of Six percent (6%) per annum on the unpaid balance, payable as follows: Commencing on April 1, 2024, and continuing on the 1st day of each and every month thereafter principal and interest payments of $577.31, with the entire remaining unpaid balance of principal and interest, if not sooner paid, being due and payable in full on or before March 1, 2034 (the "maturity date").Record a first priority security instrument (mortgage or deed of trust).

First $1,600 for origination fees, then $3,200 for MIP (Mortgage Insurance Premium), then $1,600 for mortgage security instrument, then he sent me an approved wire transfer from some fake Chase bank with the loan amount to be wire  transferred to my account.

It’s not considered a good long-term debt instrument like you may have been taught, so without the equity there and ability to resell the property in the near future for a profit, there’s really no point in doing subto. 

On the other hand, REITs and real estate notes require very little time commitment, as they involve investing in a company or debt instrument.