Like I said, we stayed outside of Salem, and wanted to spend one day visiting a pumpkin patch or farm, and another in Boston. We tried to book a car the day we arrived, but not a single booking site had availability — seriously, none. But after scrambling to download a few rental car apps, we managed to find a few options.
The only catch was all available cars were 40 minutes from Salem, so we had to get an Uber to pick up the rental car, and still return it to its spot by the end of each night we explored. It wasn't ideal, but we made it work, and having that car was SO worth it.