3D Eco-Friendly Estate Walk Through

I am helping a non-profit organization to put together a 3D walk through for a future/proposed environmentally friendly and sustainable estate. The estate will comprise of a Temple surrounded by lush gardens and water features. The estate will also contain the following following : 1) Standalone houses (for families) X 100 (They can all look the same) 2) Duplexes (for Students) X 20 (They can all look the same) 3) Library 4) School 5) Business Park (Small shops-Italian/Balinese style with cobble stone path ways) 6) Parks 7) Solar Panels and Windturbines for electricity generation 8) Roads connecting all the features 9) Estate Entrance Feature Note : 1) Design Style of Temple and houses/duplexes - Balinese 2) Use existing models and landscape objects. At this stage I do not want to create 'new' models as we do not have specifics. 3) Aim is to have a general idea for what the estate would look like. 4) Walk through is on the outside, no visuals inside the buildings are required. I do not have specifics as yet as the specifics have not been finalized. The aim is to give members a visual of what the estate would look like. Need to use a 3D tool that is freely available for future updates.