Passive income: NO

Earning passive income solely from washing cars as a side hustle is unlikely for most people. While it's possible to automate certain aspects like scheduling appointments or accepting payments, the nature of the service requires manual labor. Achieving true passivity would likely involve hiring employees to handle the washing while you oversee the business. However, this can be costly and may not be feasible for everyone. Most individuals in the car washing business are actively involved in the day-to-day operations. While there are success stories of scaling car washing services to multiple locations, these are often the exception rather than the norm. It's important to be realistic about the level of automation and outsourcing needed to make car washing a passive income stream.