The Sims 4: City Living doesn’t include the roommate system from Discover University, but you can still have other Sims regularly stay at your apartment.
The easiest workaround is to give a friend your apartment key. They won’t technically become your roommate, but they’ll be able to visit your home on their own and spend a lot more time there.
First, build a good friendship with the Sim you want to have around. Your Sims need to be Good Friends before the option to give them a key becomes available.
Then invite the Sim to your apartment while your Sim is at home.
Select the other Sim and open the Friendly interactions. Choose Give Apartment Key.
Once they have your key, they can visit your apartment without being invited.
They may show up autonomously and hang out at your home, making this a reasonable substitute for a roommate if you don’t own Discover University.
The big difference is that a Sim with your key isn’t an actual roommate. They’re still part of their own household, you can’t control them, and they don’t pay rent toward your household bills.
Use Always Welcome if you want your Sim to live at someone else’s house.
If what you’re trying to do is have your Sim spend most of their time at another household’s home, the Always Welcome reward trait can help.
You can buy Always Welcome from the Rewards Store for 500 Satisfaction Points. You can also add it with a cheat.
Press Ctrl + Shift + C to open the cheat console.
Enter testingcheats true and press Enter.
Enter traits.equip_trait trait_AlwaysWelcome and press Enter.
The Always Welcome trait will be added to your selected Sim.
Your Sim can then use objects in other Sims’ homes without being treated like an ordinary uninvited guest.
This can be useful if you’re trying to create the feeling that your Sim practically lives with another household, but it still isn’t a true roommate system.
If you want actual NPC roommates who live in your household’s home, Discover University is the expansion pack you need.
Roommates aren’t restricted to university housing. You can use the roommate system while living in a normal residential home, including apartments and penthouses.
To look for a roommate:
Make sure your Sim has space for another Sim to live there, including an available bed.
Use your phone or a computer.
Open the Household menu.
Select Place Advertisement for Roommates.
Wait for potential roommates to arrive.
Talk to the applicants and get to know them.
When you’ve found one you like, select them and choose Accept as New Roommate.
Potential roommates can take a few Sim days to appear. Once you accept one, the roommate moves in, and the advertisement is removed.
Roommates are NPCs.
You don’t directly control them. They have their own lives, personalities and roommate quirks, and some are much easier to live with than others.
They also contribute rent to the household, which can help with your bills.
The number of roommates you can have depends on the available space and the household limit. The game can have up to eight roommates alongside two playable Sims, provided there are enough beds.
If a roommate isn’t working out, you can also kick them out and advertise for someone new.
If you only have City Living, giving a Sim your apartment key is the simplest way to get someone regularly visiting your home. They won’t technically be a roommate, but they’ll behave more like a frequent house guest.
If you own Discover University, you can use the proper roommate system. Your roommates will live with you, remain NPCs, and contribute rent toward the household’s bills.
So if you want frequent visitors, use apartment keys. If you want actual NPC roommates, you’ll need Discover University.