Someone brought to our attention that the Fill Empty Homes option was not specifically mentioned for setting up challenge files. So, we added that to the General Rules...
Always create Sims in CAS (not CAS Storymode) from scratch; no gallery downloaded Sims or library Sims. All challenges begin in a fresh, completely unaltered town of your choosing. Missing community EA lots, such as the spa, must be placed at the beginning of your file. You are free to travel and/or move to any neighborhood or town. Options - all default settings: Autonomy > Full; Auto Age (Played Sims) > Yes; Auto Age (Unplayed Sims) > Yes; Sim Lifespan > Normal; Fill Empty Homes (checked).