Here's my Lil' Adventure Trailer. It is based off a heavily modified 4' trailer frame I bought from Harbor Freight on-line years ago.
Here's a build thread:
Mini Harbor Freight (type) Trailer Ultimate Build-Up Thread - JeepForum.com
The tongue has been extended, a cooler tray placed up front, frame reinforced, slipper springs swapped out for longer springs with a shackle at the end, shocks, 3500lb axle with electric brakes, 235/75/15" tires on 15x7" rims, and a custom diamond plate tub made by Diamond Deluxe (they build hunting dog boxes). And a bunch of stuff bolted to the front/back/sides of the tub. A Cabela's double sized tent-cot acts as a RTT (with a custom cover made for it).
I've put thousands and thousands of miles on this trailer with no issues. It is simple, and it works.