The Sims 2 original base game and expansion packs (from CD/DVD or ISO images, NOT Ultimate Collection) installed on Windows 7, 8, 10 cause a lot of issues. I had to buy an older laptop on which I can install Windows XP and play my favorite game.
By default, The Sims 2 allow you to built up to 5 levels. This means houses like basement + 3 floors + roof or terrace. You can eliminate the basement, or built an underground floor inside basement. There is a TRICK that allow building 6 levels: put a dormer on the highest level, but this will not allow anymore stepped roofs taller than one floor.
University Expansion Pack allows to change the floor limit: press Ctrl+Shift+C when you are in Neighborhood (NOT in a lot), type sethighestallowedlevel 16 (or any number up to 255), then open any lot and you can built more levels. If the height limit was reached, just put a dormer to unlock the limit.
This strategy is designed for The Sims 2 but can work approximately same way in The Sims 1 and 3 too. This is NOT really best strategy, but usually give nearly best results, maybe it can be improved a little… if you have more time for gaming than me to test variations of strategy.
The limit is 2100 wall segments. Half height walls are NOT counted towards wall limit, BUT you cannot build them once wall limit is reached. Foundation walls and pool walls are counted towards wall limit, BUT… you can add them even over limit. SOLUTION (trick to exceed wall limit): Delete the foundation, build as many walls as you can, then rebuilt foundation and pool.
Build mode not working, cannot build anything!
How to money cheat
How to built basements
How to design apartment lots
How to solve invalid apartments
How to rent furnished apartments
How to have more than 8 sims controllable
How to cheat and control everything
Always built houses THEN move family in them. NEVER move family to an empty lot then build the house, because only 80% of Build Mode costs are added to home value. The loss of money will be even bigger if you build, demolish and rebuild.
Complete list of cheats in The Sims 2