Nothing demands more of a truck than a slide-in camper. There will be several thousand pounds of high center of gravity weigh that needs to be secured to the truck. If I was looking for the least expensive route in doing this I would scan craigslist using searchtempest.com to find someone selling a camper and truck together. There is less of a demand as most people want a camper for a truck they already own or want a newer model year truck.
I have seen very good campers and trucks that are less than 10 years old and with less than 60K miles on the truck selling for under $30,000 and some for under $20,000. Someone owns a large camper that requires a longbed DRW truck and that camper is not going to be sought after by people with SRW trucks. Same applies to DRW trucks which are mostly used by people hauling horse trailers. Even with 5th-wheel travel trailers 80% of the time they are pulled by SRW trucks.
Great thing is that the tie-downs are already on the truck as is the camper to truck wiring so you can start the truck's engine and drive down the road. So long as it is a gas engine I would not worry about the make. Stay away from pre-2010 diesel engines as the repairs are going to be over $5,000 for injector or head gasket or other problems.
A long bed truck for most people makes it easier to find a used camper and to have a longer camper with more storage space. You will also have more options for replacing the stock gas tank with a larger capacity one in the future should you decide to do so than with a short bed truck.
I don't understand about the 6-figure price for a Class B. I have seen 3 year old Roadtrek's with the Mercedes diesel engine selling for $70k. If I was looking for a larger B+ MH with slides I would look for one on the E450 platform.
Dollar wise the most bang for your buck is with a conventional travel trailer. You will get double the living space and storage space and holding tank storage capacity and you could tow it with your current truck. For time off the grid or out in the boondocks the limitations are the capacity of the battery bank and the amount of freshwater you can carry and the amount of gray and black water you can store until you make it to a dump station. Due to weight considerations these are very limited on truck campers. With most trailers I can easily have up to 4 batteries whereas with most campers there is a space for only one and a few that have room for at most two batteries. Same applies to LP tanks and the storage tanks.
Before you spend any money go visit a state or federal camping area and talk to the people there about their RV's and what they had before and what they plan to get next. They will most likely let you check out the insides and you can see the amount of storage space, shower area, and general living space.
I went with a camper on a 3/4 ton short bed extended cab pickup because I wanted to pull into a campsite and turn off the engine and climb into the back and start cooking without a second thought. Campers and motorhomes are the best for this. I need a truck for personal use when not camping so a slide-in camper was chosen over a 28' or shorter Class B or C motorhome.
For a new truck I would go with the 3/4 or 1-ton GM trucks or the Ram 1-ton trucks with their much stiffer frames. I went with GM to get the independent front suspension and tighter turning radius (and the shorter wheelbase of the short bed extended cab version which in 2011 was only available with the 2500HD and not the 3500HD trucks).
