What you call it depends on what you buy.
The existing title will tell you what it's currently registered as.
If it's an empty van, either cargo or window version then it's simply a van. It could be registered as either a passenger vehicle or a commercial vehicle (private use ie non commercial) or as a commercial vehicle. The heavier vehicles (1 ton) are more likely to be registered as commercial than say a 1/2 ton. 3/4 ton fall somewhere in between.
If the vehicle has been commercially modified to include interior trim, captains' seats and perhaps the fold down couch/bed in the rear then it's likely already titled as a passenger vehicle.
Vans that have been commercially modified in to a 'Class B' vehicle will likely be titled as an RV.
If you buy either a cargo or passenger van and plan to modify it yourself, I strongly suggest you proceed cautiously with insurance. I'd really recommend you go to an insurance agent who is not the one who has your current policy and explore what types of insurance are available to you once it's converted. What is available and at what price will depend entirely on the state/province you are registering it in. Some are really easy on DIY mods and some are totally impossible.
I made the mistake of speaking to my own agent when I bought the cargo van. I had the insurance company firmly requesting that I find another insurance company the minute I mentioned modifying my van....
The only reason they allowed me to cancel my insurance rather than them doing it was because if they did it, I would not have been able to find insurance at any reasonable cost in that jurisdiction. I would have been blacklisted! Hence my recommendation that if you're doing a DIY - approach it cautiously in regards to insurance.
