Architectural Visualization - drone/floorplan view

I have an architectural background and can't code. I have used in the past Unity for some basic visualization (mainly import 3D model, put FPS character prefab, manage light and materials, run and walk around), but I want to make something different this time.

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I imagine to open the "game" with a 3D view (drone view) around the building exterior, with options to click on a selected floorplan and see a 3d view of only that floor (without roof/ceiling) and even further enter the floor in a first/third person camera to walk around.

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I know it could probably be made in 3000 ways, I know there are MANY things I have no idea about, but I need some starting point that can give me insight/momentum to continue researching and trying. I am looking for some asset/prefab/plugin that already has most of the components needed for something like this done, so I can just look around, edit, read and make small adjustments to scripts etc.

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Anyone has any ideas where I start from?