3 unit building with 1400sqft basement. What to do with it?

[Byron W.]

Hey everyone! I'm trying to figure out ways to monetize or at the very least, make my 1400sqft basement useful. The basement is at the bottom of a 3 unit building in Chicago that I'm in the process of closing on. It's unfinished and doesn't seem to have any flooding issues. It's pretty humid down there but nothing that a sump pump can't solve.

Has anyone else had an unfinished basement this size? What have you done with it? 

Some of the ideas I've had:

- Turning it into a paid extra storage area for the tenants and other people who would be willing to pay to store their things down there.

- Converting it into a basement level apartment (I'm iffy on this as the basement height seems about 1 foot from being able to be a legal unit. But that's from my eye and not actual measurements)

- Finishing it and using it as a Airbnb rental space

Any other ideas? Or anyone have experience with the ones listed?