Another option for those who have never tried truck camping but have a truck, time and the necessary skills is to buy a cheap old camper for the year to see how they like it. I reckon you would soon learn what you did and did not want / what you could put up with. At the right price you could virtually throw the camper away at the end of the year on the basis that you would be better informed about what 'keeper' truck camper to then buy and avoid making a costly mistake with your first 'expensive' camper.
It is an extension of the principal I used with my camper. I bought it cheaply and didn't spend any money on it for a while until we were happy we liked truck camping, knew what changes I wanted to spend time and money on and knew this particular camper was one I wanted to keep. The variation there was that we fixed up the cheap camper instead of buying a new one (we preferred the layout of the cheap camper to the new ones available locally).
But renting other vehicles has also been very useful in the past.
A fairly large class C convinced us we didn't want anything that awkward to park or negotiate narrow trails with. A tiny 4x4 pop-up truck camper convinced us that we needed something bigger than that, but of the benefits of a rugged 4x4 truck as a base vehicle. Finally the class B convinced us that we would like an interior bathroom with cassette toilet, but weren't bothered about a generator or aircon in the camper, and definitely wanted a fixed bed like our truck camper has. All very useful learning experiences for our next vehicle.
Steve.