If housing grows by more than wages, it gets progressively more unaffordable. There is no number at which it is both a good investment and remains affordable because those two things are, by definition, opposite.

Even in the best growing markets, like San Francisco, housing is still not a very good investment. It's only gone up about 8% per year over the last decade. That significantly underperformed the s&p 500.

The real reason people want to use it as an investment is that you can get it at a very low interest loan, whereas you cannot with the s&p. this has the unfortunate effect of making well-off people more well-off, at the expense of making poor people poorer.

That's not a false choice. If you grow faster than inflation than it's only a matter of time before your grow by 500% in total. If you e.g. grow by 4% annually then you will have quadrupled in 36 years.