How to build an RC motorized wagon?

It would be expensive....more money than it's worth. You can't use hobby grade RC parts like motors or servos. They won't handle the weight of the wagon AND/OR the trash. It would burn them up. You would have to use industrial motors, and those can be hundreds of dollars each. You would need a motor for forward and reverse, a motor for steering, and then you would have to make it a dump wagon to get unload the trash which would cost you another motor for that. Then you would need a transmitter and receiver. That would be your cheapest cost. It's a nice idea, kinda lazy (haha), and would be a fun project. But hobby grade materials wouldn't work. It would be a costly project.