We are not even close to "turning all the housing supply into luxury rentals." And believe it or not an 800k old townhouse is not affordable. It's already expensive as hell. Thus it's better to put 5x the number of units there, some smaller and cheaper than that. If you were to replace every single old home in the entire city with 5x the units on the same amount of land rents would very clearly go down. You're asking for San Francisco pro single family policy and that does not work. Or you can try taking a quick trip to NYC and see how "affordable" all the downtown Brooklyn brownstones are since they never replaced them with more density. And if you don't like population growth I recommend inner city Baltimore or rural Ohio.