The co-working office competition is accelerating in the Twin Cities with two Chicago-based firms recently announcing expansion in downtown Minneapolis. Industrious has signed a 20,000-square-foot lease on the 28th floor of the RBC Plaza, which sits at the corner of Nicollet Mall and S. 6th St. The news comes two months after Assemble Shared Offices announced a lease at 15 S. 5th St. for 16,000 square feet. Both companies were founded in Chicago and will open their first Minnesota locations less than a block from one another this fall. Co-working offices are places where freelancers, independent contractors and entrepreneurs share the cost burden of an office while gaining WiFi, free coffee and professional-social interactions.