A couple years ago my dad got a trailer as a gift from a neighbor. He built it himself using square metal tubes and the rear suspension from a car.
The trailer was always in my dads way, and it was too small for his PSD, so he decided to give it to me. My 4 wheeler fits perfectly inside and I can put my toolbox in their if I need the bed space.
The only things it need were lights, jack, fenders, and safety chains. All said and done I have less than $150 tied up in it. I think I'm going to go to a junk yard and find some cool wheels to replace these, the bolt pattern in 5x3.94, which is pretty common. I replaced a tire and painted it, here are the results