Also, if you know any reliable builders or architects who specialize in such projects, I'd greatly appreciate your referrals. 

Because of the larger down payment requirement for 3-4 unit properties and the limited (and expensive) inventory, it seems that we'll likely end up putting 15-20% down on a duplex.We're willing and ready to put sweat equity into a property if need be - my fiance is an architect and able to do most work on his own.  

They will be able to give you an idea of local construction costs and be able to help you find an architect/engineer to design your project.

I'll put on my landscape architect cap for a quick reply:Sawcut out & remove the asphalt at the bottom of the steps and in front of the deck, at least 2.5' in front of the deck if you can.Add a piece or two of flagstone or pre-cast rectangular stepstones at the bottom of the steps.

Also architects and engineers will need to get involved up front.Long story short, development requires capital basically from the word Go.  

I would consult with an architect who will know more than me.

You set your building schedule around the weather to keep most work happening in the warmer months.In your analysis you factor in your real estate commissions, zoning attorney, architect, site leveling, vertical and horizontal improvements, exterior and interior costs, parking, landscaping etc.

Architect? 

But it looks like the city still requires me to work with GC and architect to apply for the permit.

My name is Daniel, I'm half Latino half Swiss, I'm a systems architect and I live in Ulm, Germany.