The question is whether the well-off person moved in from the same market, or from elsewhere. (Also, whether they vacate their previous unit or, e.g., keep it as a vacation home.)
None of those are really pertinent because it doesn't change the fact that the well-off person is going to occupy an additional housing unit in this scenario no matter what.
The question is whether it's going to be new construction that they occupy or existing construction. If you're not well-off you'd want that decision to end up with "new construction" so you can move into "existing construction" at a lower rent/mortgage than if new construction didn't exist.
None of those are really pertinent because it doesn't change the fact that the well-off person is going to occupy an additional housing unit in this scenario no matter what.
The question is whether it's going to be new construction that they occupy or existing construction. If you're not well-off you'd want that decision to end up with "new construction" so you can move into "existing construction" at a lower rent/mortgage than if new construction didn't exist.