Alternatively, yes you could sell, pay taxes on the gain, and use the proceeds to help your mom directly.Would suggest for you to talk to a CPA and a 1031 specialist to confirm your best move!

Proximity to Major Northeastern CitiesBuffalo’s location near major urban centers like New York City and Boston makes it an attractive alternative for buyers seeking more affordable housing without sacrificing access to urban amenities.5.

My view is there is more protection on a wrap than a sub to and with the right disclosures and underwriting can be an alternative option. 

(Not judging the merits of the deal, alternatives, etc...)

As you're looking at properties it's best to identify multiple potential replacement properties to give you more opportunities and alternatives. 

Alternatively, OHFA's down payment assistance might work - not sure if it allows for duplexes.

Alternatively, if the bank ( assuming there is a bank) is fine with it, you could negotiate a credit and escrow the funds to be released after you do it yourself.  

Alternatively, restructure the loan with equity participation for potential capital gains treatment at lower rates.

Your goal is to build a passive real estate portfolio (we can discuss what passive means to you), so while I don't condone throwing $100k into a deal without even a basic understanding, alternatively doing so will teach you far more lessons than reading a book will.  

So, you're actually making the argument *against* debt (not for it).I think you mis-understand debt, risk and the alternatives.