Jan, I like class B's, having owned two before my current long-term B-sized class C (had it since 2006). Class B advice... Most lack ground clearance, since often their tanks and plumbing are under the floor. As long as you stick to pavement and graded gravel, they're fine. 4WD B's exist, but are pricey, and 3rd party 4WD conversions may have squirrely handling or suspect durability.
My first, a Dodge Roadtrek, was bought used with no test drive. Handled and drove very poorly, especially scary being passed by semis. 2nd was still a Roadtrek on a Chevy; drove fine, like a big heavy sedan. But _no_ ground clearance.
Be sure your test drive includes some fast-passing big trucks, and look or stick your camera underneath to find out where the low points are. A built-in generator is a plus, but adds maintenance and can be noisy. Seems that some modern B's add alternator capacity and use the vehicle's engine as a 'generator'; not sure I like that.
Black & grey water tank capacities are limited. Learn to take sea showers, and use public restrooms where possible. Paper plates. Learn about tire pressures, and 12 Volt systems.
But they're pretty nearly the ideal vehicle for going to dark sites. Warm room, kitchen, and bathroom, all right there, and sleeping space close at hand in the wee small hours.