Welcome to the forum mimihen. As for your question, it will depend on the house/lot and what it was created with. If it was made with content from stuff packs or expansions packs that you don't have, you will still be able to use it. The game looks at any lots you install and if it has something you don't have, it will substitute it with something you do have. So for example, if you download a house that uses windows and doors that you don't have, you will still have the house, but it will look different because the game will put default windows and doors in place. There are a few items that may not be replaced, but they are usually items like the pool table or different items that the Sims interact with. All building items will be replaced.
