You might want to look at a teardrop trailer. There's a bunch of plans available for them out on the 'net. Here's one websitethat offers a high-quality set of plans and guide to building one.
http://www.kuffelcreek.com/teardrops.htm
There are plans at the other end of the spectrum that date back into the 1930s. Probalby the best know is an article from a 1947 or 1948 edition of Mechinix Illustrated magazine. I don;t have link for it handy but can find it later.
H.