Yes, there is a basement.
You can put a rooftop tent on almost any item. You can tow or drive small campers. You can build your own camper from old school buses or a Nissan Versa. You can find large motorhomes that have ample space and a garage. There are also luxury motorcoaches such as this Prevost Featherlite 2007 and it has a basement.
It’s not a basement but living space below the floor which is accessible from outside or inside this rig. It’s unlikely that you would ever want to leave this luxurious interior, which is filled with chrome, mirrors and high-end materials. But sometimes, it’s nice to have a little escape. This is exactly what this room looks like, as the animated narrator shows in this YouTube video from RVing With Andrew Steele. As you can see, Andrew is on camera.
You would expect that luxury in a motorhome is not affordable. This 14-year-old motorhome with 97,000 miles and easily surpasses $2 million in value when new is available for $499,999.