I'd check local Craig's Listing under "Farm and Garden" for one of those military trailers with the pindle hitch. They usually sell for $700-$1000, are very heavy duty and have no wheel wells to cause you troubles.
no, it's a 'car' hauling trailer.
I'm assuming you've got a loader or miniex to get the boulders ou of the ground.simply place onto car hauler, drive to drop off area, use loader to remove boulders from trailer and place neatly in the 'for sale' area.
basic, tandem car haulers' will carry 6,000# easily..used/abused/need work ones can be had for 400-700$ up here. NOT pretty but would work great for your purpose.