There are some light weight models in the 17-20' size that can be pulled by a 1/2t vehicle, but the question is how long will they survive hauling any kind of weight if they are that light.
You will find most toy haulers have the axle farther back on the chassis and 15% of the GVWR on the tongue even when empty. All this to counteract the load carried in back. When you add water, many of them have the tanks over or forward of the axles to add even more tongue weight - The guys that are not hauling toys and fill up with water are usually experiencing heavier tongue weights than those that cram the garage to capacity.
As a reference: My 22' wide body Weekend Warrior was about 7500 lbs dry but had over a 1000 lbs tongue weight before I added water. It was usually over 11K lbs once I added 2k lbs of toys (on and aft of axles), 40 gal fuel (aft of axles) and 150 gal water (on and fore of axles) and the TW was around 1500 lbs even with a good amount of weight in the rear.
