[hardtke]

I honestly think this is no longer correct. Construction costs exceed the future value of the rental income stream for multifamily developments in most markets. Apparently the only projects that pencil out now are massive developments, which are hard to build in places where people work as they are already somewhat dense and don't have many empty fields. The cost of materials are going back to normal (with some exceptions) but the labor costs are increasing due to a shortage of workers. Construction costs could be slightly lowered by reducing the required quality of construction, but not by much.

[supertrope]

Land is the elephant in the room. I would be very surprised if building MDUs costs more than the equivalent number of single family detached houses. But in the majority of urban lots it is illegal to building anything but a single family detached house.