I am wondering if the interior stairs are typically removed to allow for more sq ft in the basement unit as well as greater security  between the two units?

Here’s a good starting point:Identify Your Target Market: Mid-term rentals typically cater to groups like traveling professionals, digital nomads, or people relocating for work.

The foundation was noted as good, and the foundation in the basement doesn't show any obvious signs of problems that you might typically see with foundation problems. 

Any sort of walkability is a huge plus since you can't add much more value other than a typical remodel.Good luck!

Typically we see a non refundable deposit and extension fees to keep the property tied up.

However, I’ve noticed that larger homes (3-4 bedrooms) tend to have difficulty renting as MTRs since most MTR tenants in our area are traveling healthcare professionals, typically renting solo or with one other person.

I think this because the fall is a buyers market since there are less buyers (you could get a good deal on the purchase) and the springtime in Chicagoland typically is a sellers market (you could sell for a premium) since so many buyers come in to buy.

Do yo typically get a construction loan then need to refinance out ?

You're the typical new poster here that asks for help, then gets mad when constructive feedback comes.Those questions posed will help understand where you're coming from and going.

If you need the extra funds then they're already factored into your numbers and if you don't need them then you're being even more profitable. 10% in contingency is typically a pretty safe number for this.4.