Dana,
The Class B coaches I have seen appear to be designed for a max of 2 people. I'm not in sales, I'm a workcamper who happens to be Webmaster for an RV dealer in Florida. This dealer sells Airstream Class B coaches. They are beautiful but too compact for 4 people. You could spend up to $100,000 on a Class B Airstream!
A Class C coach sounds like it would work for you. It's built on a van chassis but the coach part is wider and often has additonal sleeping quarters over the driving cab.
Use the Web to window shop. You can visit the site I built, www.sandersrvs.com and look at our Class B (1 in stock) and Class C (3 or 4 in stock) These are all pre-owned units. I think my photos will provide a sense of how much room each unit has.
Having said all this, I've often wondered what it would be like hookup a folding camper (Trailmanor for example) to a Class B like the Airstream Interstate and head down the road. I envision dropping the trailer at, say, the KOA in Needles, CA - that becomes home base - then, driving the Class B to Hoover Dam or other points of interest. Stay overnight (don't ever rush me) and then return to "basecamp."
Lew Mann, Fulltimer, Webmaster J.D. Sanders RV Center, Alachua, FL