I still haven't answered your basic question, so if you're still reading at this point and haven't taken two Excedrin, then you'll need to know your street layout, width, curb & gutter requirements to get any type of estimate from a contractor.

A popular and profitable alternative is medium term rentals or 30+day stays.

4 stainless appliances, Frigadaire, range, frig, dishwasher, microwave, about $2,000 for total package delivered.Granite about $29 sq ftnew cabinets total $1,000 to $1,500 wood medium grade, assembled and delivered

I used to have a 6/2 on Ohio State university campus north of downtown columbus and I got 1600 a weekend and netted 2500 a month probably. a lot of days were vacant but we did really well all the time for huge groups which is a nice I still recommend and there's not a lot. we just sold a new build for a medium term rental in newark close to intel. there's demand for high quality, well furnished places. 

That's ~12% Cash on Cash return which seems pretty good/decent.My concerns are by doing this, it would reduce my rent price on the main house (most likely since they'd be sharing with other tenants on the property) and also I'm unclear whether adding an ADU would negatively affect the value of the property.Option 2Consider converting the property into a short/medium-term rental, specifically to travel nurses.

@Jonathan WildyTechnically it is absolutely doable to have 1 app for Short Term, Medium and Long Term properties in one platform.

It will feed you BS for any complex analysis/task, and the more specific you are, the more specific and convincing the BS is (this is EXACTLY what I run into on Medium-High complexity code projects).

It's fully furnished and they like the idea of doing a medium term rental. 

So, what advertising mediums do you utilize?

My tenant has vacated and there is a new hospital nearby providing a good opportunity to do medium to short term rentals.