AARP Bulletin (Jul/Aug 2020) touts that you can rent your extra parking space or regular parking space when you’re not using it.
I tried 2 of 3 listed apps:Pavemint, SpotHero, & CurbFlip. Pavemint was a neat app, but had no listings, even in Chicago. CurbFlip did not exist in the Apple app store, but Pavemint was an app cool enough for me to sign up.
Turns out that if you want to rent your space, the answer is buried in FAQs. You click this link and are assigned a personal manager:
No mention of the percentage received on a rental, but you control the hours and the price.
One thing to note, your HOA may frown on this or your space might be gated.