I will not pretend to give you advice on your choice. I "RV'd "full time in a 10 year old potato chip truck in 1970/71. Had a porta potty,a hammock a wood stove and a 55 gallon drum for water.
Granted times were much much different then but it was an adventure I wouldn't trade for anything.
I would dismiss the B offhand. some of them have no practical cargo capacity at all.
If you are at all handy have you considerd a used rental or service van? Rv's appear complicated,but if you consider each system seperatly the only problem is design and placement of the components.
I don't believe you could touch a DEPENDABLE Class c for less than $20,000.
If you are up for the work and a less polished machine,you could probably accomplish your goal for much less.