Good point, and sent me scurrying back to the Airbnb details page—and fortunately, there's on-premise parking. That's good, because we're picking up the car at Avignon TGV at about 8:40. An earlier train would be more expensive and less pleasant...
We're staying at a hotel in Marseille that's just at Gare St-Charles, and considered picking the car up there...but decided that leaving central Marseille in the rush hour might not be our favorite thing...and also adds about 54€ to the rental for a one-way dropping the car off at Avignon on our way to Paris.