Hey OP, glad you finally decided to join us TS4 fanatics. I actually started with TS4 and I had all the same questions. Many great simmers have answered all your questions, I just wanted to add something that I think was glanced over.
So with TS4, there is the gallery, where simmers all over the world can post their lots and households. You can download and plop premade households and lots anywhere really easily from Manage Worlds (The maps). Plop the lots down first, then move in households with the cheat "freerealestate on" (If you are confused about cheats, check out Carl's Sims 4 Guides and Twisted Mexi's complete list of cheats). If you leave all these households as unplayed, they will continue their lives if you turn auto aging on as your sim continues theirs. (Personally I turn auto-aging on and off for unplayed sims and played sims based upon where my current sim family is in their life span). When you download things off the gallery, just make sure you have all the packs the creator used or you might have hairless sims or houses without furniture in your town.
I also reccomend downloading a complete redone save file from other simmers. Some are more popular than others, but they all take a massive amount of work to complete and put together. Some are even base game compatible. You can find save files on Sim File Share or on creators' patreons or tumblrs. Some people even leave links in the forum in the Creative Corner.
Happy Simming!
