just sell dirt
get a refiner as well so you can sell the exact same dirt in different batches of different quality at different prices for what ever someones needs may be
magnets will extract iron you can use to sell
a wash troth will extract any gold or other heavy rare earth materials
have all of it powered by solar panels and wind and water with the water filter powered by water, wind, solar
it basically would cost nothing to run all you need is maintainence such as greesing the cogs or oil occasionally if needed
always put a tarp over it during the rain to prevent rust
get silica and put it all over inside the machinery to help prevent rust