As you are going through the purchase process, make sure you check the gross vehicle weight rating (GVWR) within the context of your intended usage.
Many older Class Bs that are now in the $40,000 resale range were built on T1N Mercedes Sprinter 2500 cargo vans. Whether older or newer, you can readily identify 2500s as being distinct from the 3500s because the 2500s lack dual rear wheels. The 2500s have far lower GVWRs - once they are built out as Class Bs, there's really only enough margin left for two people plus gear. So while they may look attractive for larger groups, strictly speaking they may not have sufficient carrying capacity.
My rig, built on a 2006 T1N Sprinter, is an odd bird in this respect. Airstream installed 4 rear seatbelts in addition to the 2 that MB installed as OEM for the cab seats, but if one does the GVWR math, it's questionable as to whether I should ever aspire to carry that many people plus gear and supplies for them. Perhaps if those other 4 humans were all of preschool age, it might work. But if one goes by the numbers, it gets iffy.