There is a big difference between modelling the purchase of your own house as an investment, and the speculative investment of large banks in the housing marke

There is a big difference between modelling the purchase of your own house as an investment, and the speculative investment of large banks in the housing market. Housing prices do not have to go up for them to be a good investment for the person living in the house. If a homeowner can sell the house for the same price they got in at, then they have lived rent free. Even if they lose the interest on their mortgage, that's still likely to be a better deal than renting.