I am seeing posts where people are providing others with inaccurate information regarding drivers license requirements. No CDL is required unless used commercially, hence the acronym CDL (Commercial Drivers License). The Bus should be retitled in the domicile state as an RV or whatever the name the state uses to refer to an RV. Afterwards, a class C should suffice unless the state has additional requirements.
There are several states that require a NON-CDL class B license and possibly other endorsements (air brakes etc.). A class B is for vehicles with a GVWR (Gross Vehicle Weight Rating) of 26001+ lbs. The GVWR is NOT the weight of the Bus but the max weight it was designed to carry. Texas and Kansas are two examples of states which require a NON CDL Class B and an air brake endorsement regardless whether titled as an RV. One should always verify with the state they are licensed to make sure they are in compliance.