Some years ago, when I finished highschool, my best friend and I decided to go on a trip around the US for a couple of months before we got into college... we had plans to by an old school mini bus and turn it into a camper...
never happened, but I think I have all the plans we made hidden somewhere deep...
over all, the plan was use the luggage box underneat to house some 12volt battery for power (a lot of deepcycle battery), with a 12 to 110v convertor and there you go, all the power you need, then you get a house air conditionning unit and an auxiliary heater (both on 110v) for when temperature gets extreme and you just have to hook up 1 or 2 extra alternator on the big diesel engine (at least one to replace the A/C since you already have a backup for it) to charge all the battery when you are driving around... we thought about solar power when not cruising around for big period of time but the price was pretty high, it's a lot cheaper to rig an old fan (or I don't know how it's called, but those round thing spinning on house's roof all year long) into harvesting wind power... you also get a boost for when you cruise along... the point here is you need lots of deepcycle battery to last for extended period of time when not driving around and not having the the van to idle all the time... and try to keep your power demands low... smallest AC and Heater you can get and isolate the whole van with urethane foam to get the most out of it, you could also get yourself a toaster oven and a single portable stovetop plus a fridge (think mini bar or hotel room kindof) so you would also save on food money
With all the added weight (couple hundred ponds of battery and a single mini bar fridge plus the isolation and all) you have to build the rest out of light weight material, think PVC tubbing for all the frame work (bed, shelves, table, etc) oh and for the TV (I used to sale those, although in our plan, we didn't project to instal one) forget the plasma one, it pulls massive juice (think about 800 watt for a 50in setup) and LCD is a little less powerhungry, but the best you can get is also the cheapest and less heavy... it's LCD projection... it takes almost no power and weights nothing for a big 50 or 60in unit... but you gotta have a perfectly dark room (forget those minibus and van full of windows...)
If I get tired of working early today, I might try to open some old box in the basement that I keep moving along for many years, and see if I can get to those old plans... maybe I forgot some things...
Overall, for a limited period of time, I think it's not too crazy, I wouldn't do that all year long, but hey, I spend almost all my summers away in remote places for field work and we use deepcycle battery power all the time (to power water pump, data logger and lots of other things like underwater camera, etc...in places where generators are not an option) and I had to rig up an outlet in the van with a quick connection so we we could charge all the batteries (think like a dozen of those) while keeping the van at idle during the day and it's pretty amazing how much power you can get out of those... we sometimes had to leave all that equipment for a couple of days (that is why we don't use generator Wink ) and we never had any problem... it just took 12h for the little safari van V6 alternator to charge everything back... with washers behind the TB to get it to idle at 2000... lol