I'd like to have the ability for my sims to rent rooms from NPC households. The idea being that renting a room would be cheaper than renting an apartment. I think it would give a nice additional storyline option. Perhaps, when a played sim is moving, there could be an option on the computer / phone to look for rentals or maybe a rental interface could be added to existing NPC households that have an extra room. Just as played sims can scold their roommates and kick them out, NPC owners would have those same options, so the played sim renter would have to be careful not to upset them.
In a recent game, my sim had a roommate. Part of my storyline was that my sim wanted someone to pay rent to help with costs. Even though it helped my sim save some money, the roommate rent is a fraction of the cost. So I started thinking it would be awesome if we could have the option for played sims to rent a room from someone.