What is the mechanism under which houses would be more affordable if employees had more money thanks to the unions? Real estate (and by extension rents) will take up any available slack on income.
Employees have more money thanks to unions -> those deriving income from capital have less money -> narrower distribution of wealth -> goods (including housing) which both classes pursue are more affordable to the working class. QED.
Now, save recently, the cost to rent money for real estate was in steady decline. That means even a constant income could afford to rent an increasing amount of money. As a result, the price of housing was able to rise disproportionally to income, but proportionally to rent.
They are quite common in the UK.
Only if allowed to do so - but yes, landlord are leeches who do nothing and in return soak up every penny of income they can from their tenants.
However, isn't the typical market-capitalist argument to this, "if they could be making more money now, they would?" Don't "markets" set the price of real estate?
Markets don't, but it's really funny to me when people argue against good things, such as increasing minimum wage, with absurdities, like somehow a minimum wage increase is simply a subsidy for landlords.