[exclusiv]

That's also a key question that I ask, but I don't think a side project is necessarily important as simply finding out how they invest in themselves.

I want to invest in people that invest in themselves.

It may be a side project. It may be challenging themselves with new languages. It may be learning marketing or working on their writing. But they should be hungry. I don't run a large enough company to have to hire people that punch in and punch out [1].

Edit: [1] by punch in punch out - I mean no ongoing personal time invested in their professional skillset. I'm fine investing in people that only want to do 40 hours per week so long as they continue to spend personal time learning something.