I've only ever needed to move thrice in any TS4 save, and all three were in apartments. The first was to move to a 100k apartment bc one of the Sims I needed to complete the City Native aspiration, second was that I needed to split the household bc it was time for the roommates to go their separate ways (the rooommates I had move out I moved into a penthouse in the city), and the third was bc of more space and I wanted them in a spacious house they could afford now.
Apart from that I've always tended to just build onto their starter homes, no matter how much lot space they have. The first household I started on TS4 still uses the same starter home, it's 20x15 and although I have no more space to expand outwards, I just started building upwards or downwards. I stink at building up but I'm great at building down, so basements it is. You'd be surprised how much space you can make in a lot that small with a few wall and room remodels.
