CurtisK wrote:im wonder how heavy it will be when im finished
That depends on how heavy you build it, not on the design you're building.
If you think anything less than 3/4" plywood or a 2x4 isn't "man's wood", then your trailer may weigh 1500 pounds.
If you think 1/4" plywood and 1x1 strips were strong enough on your grandfather's trailer (they were), then your trailer may weigh 800 pounds.
You could even end up outside these two extremes, though that is very unlikely.
Andrew