We knew exactly what items we needed (including size and color, paint color schemes, countertops, etc.), and exactly what work was needed to create the vision, and we worked those costs into our construction estimate.However, you are talking about a House Hack or a BRRRR, in which case you just need to get the property into a habitable state, with some flourishes thrown in to make the place more homey and attract renters.

Next week we begin to pick exterior colors, and get started on the interiors. 

look into duct blasting test and blower door tests.

My question is should i be expecting to add plumbing, electrical, ducting, hvacs and all that into the cost aswell?

So where I particularly need advice:The outside... what is a good color scheme?

The duct work was sized at the time for an oil fired furnace .

I have verbally told my clients the information but I think I will use your list (with attribution) :):)My short verbal spiel would be 1) handy owner occupants don't need to cash flow or make money / profit and 2nd will you have a dumpster onsite the day of closing with day labor for the demo, know EXACTLY which electrician, plumber, flooring, cabinet guy, sheetrocker.....that you will use and when will they start, the PART NUMBERS for the cabinets, flooring, paint colors, doors, light fixtures.....

Kiyosaki :) The Guy has made millions by telling people that the color of the sky is blue.

We also use the same paint color for all 4 units. 

If needed, I paint everything a light, neutral color (only 1 color is best).