One could always consider buying a wrecked pickup (front end the wrecked part), then have a friend with a welding torch turn the bed into a trailer. Put a camper shell on it and you have a pretty good amount of storage, won't cost a fortune. A truck with a utility bed would give you all those neat little compartments on the sides. Or, on a smaller scale, many places, Costco for one, sell little "kit" trailers. Not nearly the usable space, but still something to think about.

If you were to go the rental route, what about your personal vehicle? Is someone else going to drive it, is it towable if it sould come to that? If not, you would need to rent a tow dolly also, thereby increasting the rental cost. If someone else drives it, you will have double (or more) fuel costs...