I'm a retired truck technician with an ASE master cert, (just means your good at taking tests). The 5.9L is a great engine, and the bus idea I think is very viable given your budget. Even though your step father has the background that he does, and the place to work, the parts are not cheap, and turning a bus into a workable RV is a tremendous amount of work, but can be done. Just start off by pricing a set of tires for that bus, cost of parts for full service of the engine and transmission, then consider all the sheet metal work you are going to need to do on that bus to make it look right. That is before you begin designing the interior. Figure six months to a year to do the transformation if you are going to do it right.
