I would now like to seek some professional guidance from an architect, residential construction contractor, etc. to first gauge whether or not my vision is possible, potential road-blocks, and alternative development ideas.

For the past 9 months I have been listening to and reading BiggerPockets material to learn how to generate wealth using real estate. Based off of what I have learned I think the following course of action is the best ...

The plan is to increase to market after 6 months.  

I've never negotiated such a deal so I'm seeking any advise. 

If they're 10 year tenants, you might have an opportunity to increase rents as well! 

We had our second home rented out before the closing.At this point and after reading numerous books on real estate, I realized that although we had reached our goal of owning a rental, our finances were completely vertical and I need to spread out to increase cash flow and reduce the impact of a vacant property.In January 2016, I started data basing different markets across the USA.

You can google "We Buy Houses in LI," call bandit signs if you see them, go on Craigslist and seek out ads who are looking for properties, or even post an ad stating you'd like to work with investors to bring them deals and locate investors that way. 

Also, any potential pay increases, windfalls, inheritances, etc are not included.

However, be careful you properly forecast for increases in the property taxes.  

So take your estimate and increase it by 10 or 20%.You don't want to invest in thin deals especially with an HML lender.