There will be automated factories orbiting in the asteroid belt. There will be space stations orbiting Mars, to serve as a forward base for maintaining the asteroid belt factories. Mars colonies will house people who travel to and from the orbiting stations. The cost of delivering a finished good from the asteroid belt to the Earth’s surface is very small. The entire global economy will shift, to one in which everything is made in the asteroid belt.
All that is needed is for someone to demonstrate feasibility; then there will be no shortage of investors. The amount of money at stake is truly staggering.