I have questions for a friend about The Sims Livin Large-
if your character falls in love with a computer character, how do you get the computer character to grow up so they can move in?
what cheat codes exist? How do I find them?
how do you move a family into a different neighborhood?
Have you tried gamefaqs.com? They do have a Sims Living Large cheat code section.
This is the orignal Sims, right? Those sims don’t grow up, except for changing from infants to kids.
In Sims 2, though, there are a number of cheats and hacks that will let you bring teens and kids under your control and let them age.
By computer character, do you mean a NPC (non-playable character) or a playable character your friend has created and could control? If it’s a NPC, you’re out of luck.
It’s much like life. You have to be persistent, but not too persistent. Offer to chat. Compliment them. Make sure they’re basic needs are taken care of. Food, bathroom, hygiene, entertainment. Offer the occasional gift, but only when they’re content enough to accept a gift. If you think they’re ready, make a romantic overture, see if it’s immediately rebuffed, and examine why it was. They’ll usually say something like, “I’m too tired! We need to talk more!”
There may be a cheat code that can make someone love you, but that’s awfully cheap don’t you think? I can see cheating to give yourself more money to buy fabulous furniture, but cheating to make someone love you? Lame! 
What’s the fun of the game?