@Cheryl Murdock the best way to find contractors is to talk to architects, designers, engineers, realtors and other investors.Also check MLS for flip properties and new construction specs for sale.Make sure to get 3 or more current project in process refinances, 3 or more current past clients, visit some job sites in progress to see how they look.

@Sarah Mason sounds like you are talking about an architect or "residential designer".

My architect warned me that it's difficult to undo this decision.

You will need it designed by an architect or engineer if your getting a permit.

My wife (realtor) and I will be handing architect/interior design and the sale of the property. 

Have you paid an architect to draw up preliminary plans?

However if I hire an architect/engineer ($7,500), get permits ($8,000) and hire a contractor ($150,000-$165,000) the price comes in closer to $165,000-$180,000.

Hi Max, I know an excellent architect who is experienced with building beautiful, modern homes with tight budgets.

I am an engineer and young investor currently I have 4 doors in Trenton and Ewing NJ area, My question today is, I have a duplex, that is on the big lot, (10+ car parking lot) and I am working with an architect and the Zoning officer planning to add to 3 - 4 more units on this lot.

For exterior extents they should have you covered, if you need an interior building survey it can often be tacked onto an architects scope for the new work.