For Icon, one of Austin’s best-known and fastest-growing startups, the luxury home represents a new chapter in its development. The company has largely made a name for itself by being the first to develop a habitable 3D-printed home and by using its technology to mostly build small homes for people with very low incomes or those who are experiencing homelessness. But it’s also scaling up to work on higher-end residential real estate projects — and CEO Jason Ballard says other companies must be involved if it ever wants to get to printing billions of homes.