[gruez]

>If the down payment was x, how are you out 20x?

right but in this case the house value never changed, so there was never any loss. Suppose the house value went down 5%, then you'd be totally wiped out (ie. you lose your entire deposit).

[runako]

Correct. You are on the hook for 1x, not 20x, your down payment. This is asymmetric leverage in favor of the buyer.

[shapefrog]

It is a fair point that for small negative changes you are getting a leverage effect (i.e. for a 1% down move in asset value you do have a 20% loss on your capital).

There is however a floor so the payout profile is a lot more like an option.