WANTED: Vehicle/RV home to live in full time

Looking for a vehicle home to live in full-time. I don’t have a vehicle which can be used to pull a trailer so it would need to be either a camper van, class C, smaller class A, or it would need to be a vehicle/trailer combo. I have a number of allergies and health issues which I have to be very careful about. I am severely allergic to mold, and also to smoke, and some animals (including cats) which means that I can’t live in a vehicle/trailer which has ever been smoked in or ever had water damage or mold in, etc. My budget is max around $20,000.