I think your PITI estimate in both cases is low.  

Interest rate is 6.3 and cash to close was $23,500.00 due to higher closing costs with DSCR loans.

(The floors are tile and terrazzo, so it is easy to clean up spilled paint.)We haven't gotten an estimate on the painting from a painter yet. 

On the surface, the deal seems appealing, but there's a catch: the asking price is $475,000, which is about 18% over the market value (based on comps and DealCheck estimates around $402,000).Details of the DealProperty: Duplex, 2,400 sq. ft., Purchase Price: $475,000 ($197.9/sq. ft.).Estimated Market Value: $402,000 ($168/sq. ft.).Financing Terms: 2% interest rate, with a 9-year balloon.Unit B Income: $2,049/month (Section 8 tenant through November 2025).Unit A Income Potential: Similar rent or higher; Section 8 cap for the area is $3,234/month.Monthly Loan Payment (P+I): $1,386.Cash Flow Breakdown (if both units are rented at $2,049/month):Gross Rent: $4,098/month.Vacancy (10%): $410/month.Operating Expenses (37.3%): $1,376/month.Net Cash Flow: $943/month.Key QuestionsWould you be comfortable paying an 18% premium for financing at 2%, especially in a market where current mortgage rates are closer to 7%?

. $38,000 would be amazing to get that, but of course, those are estimates and if it works out well. 

Raleigh specifically has introduced “Fast-Track Plans” designed to streamline permitting to build ADUs faster and more cost-effectively.

Then do a 'seismic strapping' to aid in halting further movement.IMHO this should cost closer to $20,000.

I'm having a hard time finding any estimating tools for this kind of a project, adding a story and multiple BR/1 BA, and wondered if there were any tools, sites or recommendations any of you have for this kind of a project. 

/Have you been inside the property and walked it to do a full estimate of costs?

What's the location, purchase price, expected Reno cost, ARV, etc.?