How might aliens take over our planet? If I was leading a battle fleet I'd study humanity. Then buy the planet. Hire a few human agents. Mine the asteroid belt and then sell us enough Gold, Platinum, Beryllium and other exotic shiny beads to buy up all the real estate on offer. They wouldn't need to enslave us. We've already got a minimum wage slave work force system in place. It would simply be a change in management. Nobody would even notice.