I was thinking of putting her on a month to month.I would manage the property myself, and I was thinking of looking at it with $50/month CapEx, $50/month vacancy, $50/month repairs. 

There was one vacancy when I closed on Dec. 1st.

If your seller has done some, then that is good. 3 vacancies is about 21% which is high.

I don't really see how there's 75% ROI with 220k*0.2+15k+closing=61k'ish to get in, then a gross rent of 27600, minus the multi-month vacancy for your renovation and minus PITI and the prudent maintenance and vacancy percentages.

Commercial typically costs more and has higher loan fees, plus much higher rent, so vacancy rates are more concerning, but if you have the capital, I would definitely look into NNN or at least NN. 1 tenant ideally, a national high-credit tenant, or if you want to do a strip, probably-3 tenants max to start would be the best idea. 

Run the deal through the calculators, accounting for vacancy, repairs, capital expenditures, and property management fees.

If you can do the work while they are living there you'd have less future vacancy, and they are even more likely to stay.

During a vacancy, when there is no income is also the time when you are writing checks to prep the unit for the next tenant.

Specifically heat and water for a triplex in lower Westchester, NY.Additionally, as I had mentioned before, my idea behind purchasing a duplex rather than a triplex is that my major goal was to constantly have 2 of the 3 units always rented and allow the loss of one unit to count for my annual vacancy rate.

Make sure they also understand what the taxes are going to be like and to be honest, if they can tell you vacancy rates, they are probably lying.