I'll offer what I've learned. Last fall I was in a similar boat and feel like my purchase decision was a poor one. Basically, I wanted a 4x4 camper van I could spend a lot of time traveling to remote places in, both winter and summer.
What I Did: I purchased an older 4x4 van. The van, now named Polar Bear, was nearly empty aside from some trim and two bench seats. It had a lot of mechanical issues, considerably more than I understood it to have when I purchased it. I picked the van up for $3250 and have probably invested thousands of dollars in repairs. My grand total is probably floating around $17k now and I have not started the interior build. You can read about my build here:
Note that the tab I've accumulated includes new paint and wheels which comes to nearly $3k alone. Additionally, I had to have extensive work done to the drive train which killed another $4k or so. Then there were odds and ends including the a/c, new radiator, windshield (was incorrectly installed) and more.
The lesson: Once I was invested to a certain point, I couldn't get my money back out of the van by selling it... so I was sorta locked into the path. I thought I could save money with this route, but I bought a money pit.
What I should have done... If I had it all to do over, I would buy a completed Sportsmobile 2wd and have it converted to 4x4. This seemed too pricey at first, at around $12,000 for the conversion from a local shop. In retrospect, I could have picked up a fairly decent rig for around $8k and converted it for a total of about $20k.
The upside to this approach is the fact that you end up with half your drive train being brand new and under warranty. Additionally, my dated 4x4 conversion will never perform remotely close to the newer conversions. Mine is also full of custom fabricated components that will be considerably more expensive to repair. Quad van, in particular, uses a lot of stock parts - making future repairs a lot less painful.
Building the "camper" part: Doing the camper build out is extremely time consuming. I've done a few things such as building door panels, replacing the stereo system, installing a rotating seat, etc. I've done a lot of research on electrical systems, fresh water systems, propane systems, waste storage, etc. New parts get expensive fast. I think finding a completed camper conversion would be a huge time and money saver.
That is, of course, unless you really want to do the build yourself. In this case, especially if you have the time, you can have it however you want it. I'm hoping to take full advantage of this and do a relatively unique design inside. I'm really looking forward to this part of the project. If the idea excites you, then I'm betting it will be worth the time and money.
I come from a background of do-it-yourselfers. My family built our home from the ground up in 1990. We started with a wooded patch of 17 acres and build everything but the cabinets ourselves. It took us 7 months of hard work to get "in the dry". Every time I visit the house (which my parents sold just weeks ago) I remember what went into it. It's kind of a nice feeling.
I know I'm a bit all over the place, hopefully something in there will be helpful.