I have some experience with cheap trailers. I've had one of the cheap 4' by 8's and a old used snowmobile trailer. With a cheap trailer, I would be wary of:
*low load rating on the axle: easy to bend if you overload it.
*small wheels: they spin faster so you need maintain bearings more often. worrisome when you hit potholes larger than their diameter. limited ground clearance.
*weak tires: easy to flat on crappy roads.
*weak frame: will crack at the welds eventually.
All that said, if you maintain the bearings carefully, carry a good spare, avoid bad roads, and don't plan on keeping it very long, these will work fine. I ended up getting a used '09 aluminum tilt-bed 8'x10' snowmobile trailer with 15" wheels for $1300. I have a older flat-bead trailer with re-welded frame, 1 new bearing, and new lights for sale cheap if anybody is interested.