Consider property taxes, utilities traditionally paid by the owner in that area (water, trash, electric, gas, ...), repairs, maintenance and landscaping, costs to service the loan, etc.If your friend would become your tenant, would you be willing to raise the rent on her? 

Sub2 on a heloc is probably trickier since they can be called even easier than a traditional mtg, aside from the due on sale clause.

Traditional financing is probably out because of debt-to-income ratio.Anyone know the pitfalls of getting a HELOC in New York, or have any preferred lenders?

Aside from what Roland mentioned about the traditional path of selling, sometimes the seller is another investor who just wants to unload their properties, other times they are adult kids who have inherited unwanted properties to not have to deal with the costs of it.

What are some of the challenges that you have faced in the past when educating investors that may be more inclined or versed in the traditional real estate asset classes, Such as SFR, MFR, etc... 

I was able obtain a traditional loan with a $1,200 mortgage payment, while I rented out the three rooms I had available for a total of $1,450.

These contracts are facilitated through what is called "double deposit escrow", as opposed to a traditional escrow company. 

Get preapproved with a traditional lender if possible, if that doesn't work out come back and ask again.

You need to save more if you are planning on not using an FHA, for reserves at the very least,  You can try owner financing but it will be difficult to find and often will be more expensive than traditional financing especially in the long term.

Originally posted by @Christian Hutchinson:I found a small apartment building.