If I had the space to store one, I'd get a used ambulane or Red Cross/Salvation Army ERV or the like. I do know that the ERVs tend to get replaced in shall we say "better" condition than most box back ambulances, brcause they tend to SIT, and SIT in some counties, and then get replaced by AGE from funding by the nationa "Hey, it's 14 years old" (and yeah, it only has 5-10k miles on it)

Some have stoves (around here, the Salvation army trucks), all have counters, most have commercial radios mounted, but will be stripped on the way out, but at least the wires will be run (Red Cross is in the VHF 'low' - aka 50 Mhz band)

One thing you will find, surprisingly, they they get crowded, fast. The 2 groups I belong to that have one have found that they really really want to invest in the "tents" that attach over the rear doors (you will see them on Telco "box" vans if your area has them