I added a 2nd bedroom to a one bedroom apartment we have for a rental property. We partitioned off a portion of the extra large living room to have the space for the second bedroom. Subflooring was put down first to level the room and a closet was built into the corner. Drywall was installed, finished, and primered for paint. The living room light was moved to the center of the new living room area and the hole from the previous light location was patched. Rerouting the ductwork for the furnace was the only part of the process that was subcontracted out.