There are three main co-ops in this system. Development, operating, and financing.
The development co-op finds land, purchases it, and arranges for the construction of a multiplex on it. Its members are people on the waiting list. It also manages that list by interviewing prospective members and dealing with member loans and escrow money.
The financing co-op sells bonds and writes mortgages.
The operating co-op runs the housing co-op.
There are other possible co-ops. Parking and heat pumps might be separate if the neighbours are invitedd to be part of them.