I've got a 5x8 Carry-On utility trailer like this one: http://www.carry-ontrailer.com/products/show/5X8G/
They sell them at Tractor Supply, Lowes, etc. for $550-700 depending if it's on sale. Put down 1/2 plywood over the mesh floor and you're good to go.
It's only 350 lbs., and has a fold down rear gate, loading doesn't get any easier than that. Easy to tow with any vehicle, including my Mazda 3 hatch.
Carry-On rates it as a 1650 lb. payload, more than enough for 2 heavy or 3 light bikes.
If you can live without a folding trailer these work great for the price, and can haul anything other than bikes too.