Designing a interior for horror game... Need help :C

I’m a newbie in unity 3d so i need help :<
I want to create a horror game, which will look like a left hospital/mansion or hybrid of forest and a house.
Such as Outlast and Slenderman at one. But i have no idea how to design interior of this hospital/mansion. Please don’t tell me to try 3ds max or such because it’s too complicated for me :c (as i said i’m newbie) I don’t want this game to be super high graphics and long, i just want to create my first indie interior game.
Or should i try to make it with blocks in unity ?

If you don’t want to learn how to model your own assets, you’ll have to acquire them from someone else.

Fortunately, the Unity asset store makes this really simple - here’s the first hit I found:

unity’s cubes is very good to use its not to hard to place them to shape your hospital/mansion. You could also attach a texture to it and don’t forget we have the asset store and if you want I could make some models for you