You have to add site works (prepping the site, connect utilities, permits, etc) most of these costs are really unique to the site but assume 10-20% of the construction cost (30-60k) plus the cost of the land, architects, engineers and financing costs. 

Once the 2040 comp plan is passed and they begin working on the zoning change for ADU's, I will have my architect draw up a rendering/schematic lthat can be somewhat universal and start the process.

Is your agent including water tap on fees, architect fees, interest accrued on your HELOC or just the flat building cost?

Actually, this property in particular (and many many others across OKC) are owned by the same gentleman who's son-in-law, a successful architect, has taken over and is going to be putting a lot of money in them over the coming years.

Hey there,A colleague is in need of an architect in the south/southwest suburbs to design for a commercial/retail space. 

Next you will need to put together your team: architect/designer (even if you are going with an off-the-shelf design); contractor; financial team, etc.  

The structural engineer, the architect and the building will all have their information there.

In Long Island, I am currently trying to figure out if I can convert my garage into another legal apartment and am using an architect to help me.

You'll need an architect to prepare plans that would be submitted, reviewed and eventually approved by the building department as part of issuing the permit.  

Also, you will need to hire an architect or engineer.A kitchen may need a grease interceptor installed.