If you do not plan to tow anything heavy and do not want 4wd, a Class B RV may be a better solution for you. There are small truck campers made for 1/2t trucks, but expect them to have smaller tanks and not be as robustly built.
I would recommended a 3/4t truck as minimum just for the upgraded axles and brakes over the 1/2t models. As others have posted, many manufacturers will skin their vehicles with the the same panels and you have to look at the underpinnings.
I had a short bed extended cab 3/4t diesel truck that was just over 19' long. With the camper, it was under 22' allowing you to fit most parking spots. We were on the heavy side because wanted a slide out, the largest available tanks, generator and dual-pane windows (about 11,500 lbs when fully loaded). Going without the diesel, slide and generator would put you closer to 10,500 lbs. This weight puts you in the range of most modern 3/4t and 1t trucks without going to dual rear wheels and still keeping a small profile.
