The duo behind Bows & Arrows is reinventing the business in a new space devoted to nurturing local artists. In spring, artists Olivia Coelho and Trisha Rhomberg plan to open a new concept rooted in the vintage clothing store they've operated in Midtown for three years.  Coelho and Rhomberg, who are both clothing designers, will continue to sell vintage and repurposed clothing at the new space at 1815 19th St. But Bows & Arrows' new location will also be a place for the creative class to eat, drink, sell art and be exposed to other talent.  "We're the poorest philanthropists you'll ever meet," Coelho said.  Coelho's parents bought the building in June. Coelho and Rhomberg will lease it