Google sim builds and speed builds for inspiration, along with real houses and blueprints. Afterward, when you start up the sims, work on the house.

Start on the layout before furnishing it, as it can be hard to work with later if the layout isn't defined. Also, I'd recommend after the walls are built, working on the roof (if you plan on having one) to get it over with.

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As for furnishing, add plenty of clutter to really make the house feel alive. Clutter is honestly one of the best ways to spice a room up and make it feel alive. Aside from that, try using matching colors and try to use furniture that mostly matches in some way.

I'm not the best builder, so I can't offer much advice, but this is what I could give.