AutoCad Small House Construction Drawing and 3D Rendering

I need a house measuring about 420 sq ft with 2 bedrooms and 1 bath. The design will also be mirrored on the lower floor so that both floors will be two identical apartments. The building is for a hot, wet tropical climate. Mechanical ventilation is not an option, so there is complete dependence on natural air circulation. The building code requires 2 entrances/exits. There should be 9 columns that measure 9"x 9" and are made of rebar-reinforced concrete. The building envelope and floor are of 8" wooden boards, and the partitions are of sheetrock. For moisture resistance, the bathroom and kitchen areas are to have concrete floors and concrete block work for walls. Staircases are of reinforced concrete. The roof is to be of a shed design (not the gable design shown) and covered with metal sheets and have a drywall ceiling. Rafters are of 2"x6" lumber. The sketch attached is a suggestion. You may use flexibility, creativity and initiative in your design. I am also attaching an approved drawing for code reference and to show what's acceptable here and the conventions used in my country, St Lucia. For the rendering please show the building on a land slope gradient of 1:3. The color should be varnished wood and white trims, windows, doors and framing. Because this is economy housing, the focus is on keeping construction costs to a bare minimum. If the drawing can be done using LibreCAD, then I can later make alterations myself as I am trying to learn how to use this software.