What sort of size range are you thinking of? How much stuff do you need to carry about? Does it need to be enclosed? Is the trailer just for transport, or might you be working out of it as, say, a food trailer?
If it's a lot you'll be toting around, do you have or will you get a CDL? (Basically a CDL is required if the total registered weight rating of the trailer and tow vehicle is over 26,000 pounds. RVs used for personal noncommercial purposes are exempt from this requirement, but that wouldn't apply to your use for business/commercial purposes.)
Full-size vans make pretty good and capable tow vehicles for bumper-pull trailers, at least if suitably equipped, and can of course carry a good bit of stuff themselves. Often they have greater payload than pickup trucks of a similar class. Trucks might generally be a bit more maneuverable, and for large trailers a gooseneck/fifth wheel setup has some advantages that can't be had with a van. But in your shoes I suspect I might be looking for a van...or maybe a smallish box truck. It's very hard to guess without some idea of the scale of things involved.