There's a large grey area of old/marginal/condemned housing stock where buyers are making a tradeoff between a teardown + rebuild vs buying an old house and patching it up.
Flippers who successfully rehabilitate an old house do increase the effective supply.
Where I live (UK), I think most young people would be grateful for an increased supply of cheaper rundown houses to buy. Done up houses we can't afford don't help at all.
There's a large grey area of old/marginal/condemned housing stock where buyers are making a tradeoff between a teardown + rebuild vs buying an old house and patching it up.
Flippers who successfully rehabilitate an old house do increase the effective supply.