I would think long about the issues that can arise with a rental of your machine. The people who want to rent typically have no clue as to the ins and outs of longarming, and would require you to be on hand for the issues that will come up. Think about your learning curve going all the way back to the loading process.
Requiring them to have a learning session first is a good idea , but not everyone remembers everything...
One shop near me thought they would rent out time.... after 2 weeks they quickly rescinded their offer/plans. All it took was one customer causing big $$$ for a repair and they were done with it. The addional cost of being out of commission to do their own work only added to the reason they stopped.