It is pretty easy to make a Prowler clone from the kinds of beginner benches you get from Sears. I picked one up from the local Cragislist (the lady was giving it away for free), and then spent a few hours cleaning it up, disassembling it, cutting it down, then putting it back together. I paid a guy down the road a few bucks to weld skids on for me, then hit it with a can of spray paint. The pipe that holds plates is just pressed into a PVC endcap bolted through the frame. There was really nothing tricky to the build at all.
As has been said already, the surface you push it across will determine the amount of weight you need. I've had up to 115 on this thing, and it is plenty sturdy.