Impossible to say without knowing the loan program, and lenders have overlays, but 6 months of payments (PITI) is a good ballpark rule of thumb.

Cool thanks for your replies because I built a platform www.allmetrorentals.com  and its been hard to get users to list their properties and to get a MLS Agreement for a IDX seems nearly to impossible because I don't know any brokers personally

Thirdly, its comments like yours, telling people to watch their tone on a forum where its nearly impossibly to tell what the tone is unless it blatantly obvious, that make people more likely not to comment than me questioning a finance strategy that was lacking some key piece of information.

On the investment side finding anything with an upside is becoming increasingly difficult and finding affordable housing that is not a trailer is near impossible.

It is not impossible I am sure, but those house-hacks where you get paid  to live in MFR seem to be rare here. 

I really want to invest in positive cash flow properties but it's impossible in New York.

Those returns look ok without having to put more money in to it but not knowing how much the renovation costs will be it's impossible to say whether it's a good return.

And finding a duplex is almost impossible up here so I feel I shouldn't let the opportunity pass...but at what cost?

I wanted to start with Airbnb’s but there’s really not a huge market for them here except for in New Orleans but they changed all the rules and regulations recently so it’s impossible to do it there.

Non-substitutable is similar to rarity, but it also means that what your posting is relatively impossible to be replaced by something new.