The Sims game should have the option to make some members in a household NPC. Think about it.

The last roommate my Sim had baked cakes. There were 8 cakes in fridge before I kicked her out. She lived there maybe 10 hours. All she did is bake white cakes. Sorry, I need to control my Sims. If you can't focus on a lot of Sims then just play smaller households. Also, it's easy to move Sims in and out. If they a related or good friends they will come over and hang out all the time anyway. I hated that I couldn't control the pets so I have the controllable pets mod.