Happy, while I think you're project is "doable," I do not think it is practical, unless you happen to have all the required materials on hand and can fabricate and install the metal container yourself. By the time you purchase 4 wheels, tires, and axles, plus the metal to build the bin, and then pay someone to do the work, you would wind up with a marginally useful and very expensive cart. I believe it would be much more practical to purchase a two-wheeled wheelbarrow or a four-wheeled garden cart, either of which can be procured in the $50 to $100 range. You might pick up something suitable off Craig's List for pennies on the dollar. (I prefer the 2-wheeled wheelbarrow; fairly easy to push and dumps easily, too. However, the 4-wheeled carts have the advantage of bearing all the weight, so that you don't have to lift any of it.) Check your local hardware store, garden center, big box store, or even Amazon.