There isn’t very much to comment on with the key and shelf models, but I have a thought of a couple suggestions for the door.
I think it would look nice if you darken the color a tiny bit where those divots by the bottom are, to help simulate the depth. You can place a new thin part inside there to color instead if the door is all one piece from unioning. You could also build a thin frame piece around each of the six windows that is slightly thicker than the door itself, to also give the model some more depth and detail.
You’re on a good route, try to keep things proportionate (door especially), it’s kinda too wide and the doorknob too small.
I suggest working much more to get a feel and then using these things as your “building resume”, selling models I have no experience with but I don’t think I’d want to buy solo models unless they’re like designed specifically or just really complicated.
Also make sure to check out free textures on the internet, they’re handy and can come good, especially with the texture offsets in ROBLOX.