The half duplexes in the same neighborhood are selling for $600k.Besides Landmarkk, the leading Tandem House architects in Denver are:Becky Alexis (mainly NW Denver)Niccolo CasewitBrian Pearson (Denver and all Suburbs)Kung Architecture

All ADUs still need to be title 24 compliant, licensed architecture plans and subbed out work which need to be completed by licensed tradesman.

Do you have the set of architectural plans in hand? 

For the new construction project, we ended up doing the architecture/design ourselves (my wife) and then hiring a company in Frederick that specializes in turning designs into architectural drawings.

How much do reasonable architect charge for this kind of job.2)What money should I be looking to pay for this remodel and addition.3) How easy is to get permits with cover situation4) Any other advice to make this task smooth and efficient.Any referral for architecture firm to help with this job. 

At least in NY its almost always requires every unit to be "fire walled" meaning every single unit need to be an encased shell with double 5/8 dry wall or... you need a sprinkler system, all of this requires architectural plans and an investment of $5,000 (ish) to find out its cost prohibitive to do it.  

Views are amazing and unique, and the site offers some incredible architectural opportunities.

I know structural super well and have been studying a bit of residential architecture and doing plans in Revit etc.Feel free to reach out!

Does the property fit into the architecture of the portfolio you want?

Architectural shingles will cost more than 3-tab.