Building a house in GTA V

[B747Man]

So I see lots of cool looking houses on this site and thought I would love to make one for myself. What I would really love to do is make a penthouse at the top of the maze bank building in downtown. I live in LA and have always liked that building. I have used mods before, but I have never built one myself.

So how hard would it be to do something like this, and what is the best editor to build it with? Also, would I need to learn any scripting? If I can, I would like to have a place that always loads when the game loads, so I don't have to do it manually and maybe be able to watch TV or smoke weed.

Thanks