Those numbers do not seem correct, unless you are using terms like loan amount of $104,000 is the unpaid principal balance (which is the amount that accrues interest), and the $270,000 is the total payoff.There are two components to a mortgage statement - the first is the reinstatement amount - this is the amount to bring the loan current.

I then hired an architect (or at least I thought it was an architect) to use the CAD file from the surveyor to draw the proposed addition to the house by using the surveyor's site plan.

You are subject to failure to file and failure to pay penalties.

You are simply just going to be paying your accountant to file 3 tax files for 1 property. 

You are still getting principal paydown and appreciation on your investment so coc is not your true return. 

As it is, I've gone back to just keeping paper receipts in a file folder and electronic receipts in a gmail folder.

I've included an example below to help illustrate this.So different lenders have different rates (which do vary even for DSCR loans) but these are factors they all consider.See example below:DSCR < 1Principal + Interest = $1,700Taxes = $350, Insurance = $100, Association Dues = $50Total PITIA = $2200Rent = $2000DSCR = Rent/PITIA = 2000/2200 = 0.91Since the DSCR is 0.91, we know the expenses are greater than the income of the property.DSCR >1Principal + Interest = $1,500Taxes = $250, Insurance = $100, Association Dues = $25Total PITIA = $1875 Rent = $2300DSCR = Rent/PITIA = 2300/1875 = 1.23If a purchase, you also generally need reserves / savings to show you have 3-6 month payments of PITIA (principal / interest (mortgage payment), property taxes and insurance and HOA (if applicable).

Historically speaking, STRs will at least allow you to cash flow right out of the gate and when you add in the appreciation and principal paydown and tax benefits, the returns are 40% a year or better on most of these deals. 

If I invest a multifamily through a Roth IRA, will I still receive the same tax benefits as I would with personal cash when I file my tax return?

It just seems like there will be many that fail to file their report and I just can't see the government really going after tiny businesses for so much money for something that is so easy to forget to do.