What happens if the service truck can't reach our unit because of parked cars?

A unit 20 feet off the curb is an easy reach, so parked cars across the street only matter if they leave the truck nowhere to stop near your driveway. The driver doesn't need to pull onto your property. They stop in the street, run the hose up the driveway, and pump from there. When we gutted our bathroom last year our unit sat about the same distance back and the driver never once came up the drive.

What actually turns into a missed service is the vacuum truck having no spot to stop at all, or a car parked in your own driveway between the curb and the unit. Keep the driveway clear on service day and leave an open walking path to the door of the unit.

Call the rental company and ask which day and rough time window your route runs, then give the neighbors a heads up for that morning. In my experience a driver who gets blocked calls or swings back later in the route instead of just leaving. Ask the company how they handle that before it happens so a blocked visit doesn't land on your bill.