If you’re patient you can find a van with around 100K miles for around $5,000. They’re out there, but it might take a lot of time to find, and there may be a few solvable issues that need to be taken care of. My van with 110K miles cost $4900, but I knew it needed ball joints, tie rod ends and tires. I replaced the ball joints and tie rod ends myself, had it aligned, had the tires replaced, replaced all the fluids and several wear items, and then proceeded with the build. In all we have around $10K invested plus our time. Now we have a van that can take us anywhere we want. Our van is a 2000 Ford E350 passenger model with the long body.
I’d rather get a passenger van because they seem to be better taken care of, and those who drove them probably didn’t abuse them as much because they’re carrying passengers. It also already has some insulation if you’re okay with the original interior, making the build much easier, and I really like having windows. I think the whole “stealth” thing is a crock because people become very suspicious when they realize that someone is trying to hide in a van. Better to be open and honest about what you’re doing.