> Landlords don't create added value. I'm skeptical that it is a necessary service; housing is necessary, but is renting housing necessary? Why would that be?

There are many cases where this isn’t true. Many (most) residents in urban areas are transient. They stay for a couple of years, get married, then move to the suburbs or another city to start a family.

There are a bunch of other reasons why someone wouldn’t want to stay in a location for a long period of time.

Rentals absolutely make sense in this situation.

A house costs more than some people have. Without a rental market, those people become homeless or completely dependant on government. Neither is desirable.

Without the profit incentive, what developer would build a multi unit apartment building to achieve higher density living in cities?

I'd say a house costs more than almost anyone has; it's why people need to take out loans to purchase them. That said, without a rental market the price of houses goes way down. As a result, the people that cannot afford houses then are mostly the same people that cannot currently afford rent. This is because the mortgage payment and insurance for a home is actually lower than the monthly rent. If the top value were lower, it would be a safer risk for a bank but because it's so high, people don't have that access to credit.

A developer still has a profit incentive; mostly the same one they have now, actually. They sell the apartments.

So you have a city like Los Angeles or NYC. You convert all housing to single family homes. Can more people of fewer people live there now?

Why would you convert all housing to single family homes? Do people not own apartments for some reason?

>That said, without a rental market the price of houses goes way down.

I see that you are saying you would simply sell the apartments instead now. What is the solution for (e.g.) new grads who do not have a down payment yet? Why aren't tenants currently pooling their money, purchasing the properties they live at and converting it to a Tenancy in Common?

I do not think prices will drop without a rental market. Prices might even increase because you are making the market much less efficient. It will also make building new units more difficult as there will almost always be a holdout in the building.

>Landlords don't create added value. I'm skeptical that it is a necessary service

Subdividing your land and making it available to others is valuable. The world without that is all single family homes.