Many well-intended regulations push against the creation of small apartments. Changing the plan to have two 300 sq.ft. units instead of one 600 sq. would cost n

Many well-intended regulations push against the creation of small apartments. Changing the plan to have two 300 sq.ft. units instead of one 600 sq. would cost nothing in building material, but both those flats need two exits (for good fire reasons!) so you add another staircase, and both may need parking (by local law) so you add another 200 sq. ft. outside (per floor), and maybe they all need to be wheelchair accessible (ADA) so maybe you need a second lift, or extra corridors... and suddenly the small units aren't 50% the rent, but 80%, and so they don't get built.