What do you think happens if a character in an apartment you aren't playing has a job? Let's say you're playing Family A in the same apartment as Family B. If the mom in Family B has a job at 10:00, can you see her leaving the house for work at that time? I think that would be pretty cool. Does anyone know if this will happen?

Yes, they will go to work. Kids will also go to school. So if you have children in family A but you are playing family B you will see the school bus arrive and take the kids to school.
But yes, they will leave for work.

i wonder if they will ask your conrolled sims to leave? especially like if they arent best friends left..maybe its just me but i wouldnt lets just any old person say alone at my house/apartment but i guess its safer as a sim not like theyll pick up the tv and leave