I would suggest talking to an architect if you get serious about adding space.

Here's a few market segments I think you have room to further expand on-commercial/ institutional developers and investors- appraisers- architects- engineers- Wall Street (real estate private equity funds, debt funds, reits, investment banks)I'll leave you with how to bring all these members on an entice them a bit but id love to see some of the conversations that would result.

I am confident I will need an architect to maximize existing space .

This won't include the cost of land, or any major electrical upgrades from the city, and won't include the cost of an architect.

And oddly enough I have done some work with a local architect and although I wont actually build a duplex for 70k, it wont be terribly far from it.

I'll also note that this is a little unique because I'm a licensed architect and I'll be using my stamp for some of these projects, so the architecture firm needs to be its own business (and the requirements for that are much more stringent), making this is a little more complicated than normal. 

not sure who does work like this2. new roof design (probably 2nd floor redesign too) - architect or structural engineer3. framing of new roof and 2nd floor - builder?

(4) What architect/builder do you recommend that has a variety of build plans to use as a template or starting point?

We don't get call backs, we are on budget, and we handle pulling all of the permits, dealing with architects, and any other management that comes with construction. 

When getting an acqu/construction loan, how can you really know your costs/budget until you have construction docs from the architect and send them out to contractors to bid.