Welcome to the madness! The best advice I can give you is to read this entire site, stem to stern. There is value even in reading the fourth argument about whether or not to take out your interior ceiling panels (take them out), or flush toilet and black water tank vs composting toilet (composting).
By the time you're done reading you will know exactly what bus you want, where to find it, and how to evaluate it when you find it. No matter; you will eventually fall in love with some other bus and change plans. But have a plan; it helps.