If you don't mind saying, what did you pay to do the gas and electric meters? 

If I got a Heloc, once the property is built, could I get a traditional mortgage and pay off the heloc and then tap into the new equity as well?

There will be some giant surprises to many there when you have to start paying engineers for frequent evaluations and making the structural repairs required.   

The previous owner was paying $3k a year with DB. 

I'd just reconsider the economics and pay someone to do some really good underwriting and if you don't understand zoning I'd get a zoning attorney. we self perform all of our own zoning 

In New Jersey, the tenants pay the realtor fee so you aren't out of pocket on that.

It's a bummer that I can't even pay for it!

You'll pay a bit more in points/fees but if the deal works, they can get it done.  

I agree with the other responses so far and will had some info where I can.I am not too familiar with the DC market, but from my understanding there are plenty of high paying jobs there to support rents.

Paying off a house completely is a trap.