@Vince Padalino I am starting off in the Elizabeth area and probably making a mistake trying to manage this duplex myself but more to the fact I am going to need to replace the heating system (steam boiler), do you have any companies that you can recommend for this work and or HVAC? 

I was looking for the same type of returns in the NYC area (was focused on Queens) but from the ~30 deals I looked at, the very best were ~7% cash on cash, and that's if you can get a below-market offer accepted and can do some rehab work.

Example: in NYC, say in Queens, an average 2-family brick house in a C+ neighborhood will cost $800K to $1M.

Your not going to make much month but as more people are pushing from Queens to Nassau and Nassau to Suffolk the closer you are to Queens seems to be the better rent you can get.

Not sure if you are considering the Queen City, but I thought this article would be helpful.

Queens (LIC, etc.) - you will likely do better dressed more "hip".

Hey Elizabeth, yep... not really hard to do. 

The list of stuff I have to provide is long and costly including new queen size beds.

You said you live in Union county, Elizabeth and Plainfield are good options for rentals.

They can do a single King or 2 queens at a time.