I'd be a registered driver like an Uber driver. I go to a Fedex/UPS/USPS shipping facility, ask for a couple of packages to carry in my car/truck. I deliver them by days end and I get a cut of whatever the driver would make per hour. All packages would be registered to me so if I failed to deliver them, I would be held accountable.

Honestly, I'd stop by after work, grab a few packages that are on my way home, go and deliver them to the door, snap a picture of the package at the door and upload the photo to the app, then go home. Adds maybe half an hour to my commute home, and make some extra money.