I just bought the dump trailer pictured in the atttachment on EBay for $1,800. Better yet, it's located about 60 miles from my property, so I can easily pick it up.
It's 6' x 12', rated at 12,000# GVW, has self contained electro-hydraulic dump, brakes work, tires are OK. The floor of the bed is rusted at one end but I can weld in a patch.
I can pull it with my tractor on site, and I can pull it with my Dakota when loaded up to about 2,500# (5,000# total), which means I can use it to haul stuff to the landfill or transport my tractor, but I won't be able to use it to haul full loads of shell rock or fill until I get a bigger truck. Off to look at trucks.