Generally, cleaning and painting on the same surface are not done same day to let it dry - commonly, a painter will do his planned painting for the day and let it start drying for the next coat, then go to another new jobsite and spend an hour or three putting down tarps and cleaning and prepping and masking and maybe priming if needed. Then next day paint or prime (if needed), come back following day for second coat, etc.
So, for your size job I would say 3 days minimum for a 2 man crew including the prep and priming part day, for one coat without differing trim or door paint or finishing - more like a week if needs priming and two coats - like for white over black or magenta, up to two weeks if stained/clear finished trim or doors and doing them too. It could take a single-man contractor a week or more depending on if doing ceilings or not, up to three if everything including clear finish stairs, doors, etc.
Very rough estimating - if in decent shape and few nail holes to patch etc, for a normal apartment you can figure around about 150 SF/manhour for ceilings unless heavily textured then 80 or so, and about 100 SF/hour for walls, and about 1 door with trim per manhour, and from 2-8 manhours per staircase (normal size) dependign on number/type of banisters and such.
Check out the Home > Painting link under Browse Projects (at lower left) for typical interior painting costs.