If you ever wanted to build yourself a decent, hard-sided camper trailer, for under $1000, then check this out.
It is based on this trailer. He had a number tips about the building process. Putting bubble levels around the trailer and using the stands are apparently crucial during initial construction and later when setting up for camping. This is due to flexing of the trailer. You can see his solar heated hot water tank (the blue jug wrapped in plastic). Also note the solar panels behind the trailer.
It has all the amenities, including a shower, sink, and portable toilet. Looks like it sleeps two comfortably. When it is folded down, the wind profile is extremely low. That and its light weight make it very easy/economical to tow. He pulls it with a Geo Tracker!