Is "set some time on the side" a common phrase?
As others have pointed out in the comments, aside was likely the intended word. On the side usually means something in addition to ones current activities, such as a side hustle, or a freelancing gig.
As others have pointed out in the comments, aside was likely the intended word. On the side usually means something in addition to ones current activities, such as a side hustle, or a freelancing gig.