Quote Originally Posted by Junjie View Post
Just for perspective - not suggesting Detroit is anywhere near this point - it actually works the opposite in some really high-value real estate areas. For instance where I live outside DC [[Arlington), developers trade additional affordable housing units for the right to to build more total units. The county says "typically we'd only allow a ten-store building here and we'd mandate X affordable units, but if you add Y additional affordable units you can build 14 stories" and almost inevitably the developer takes that deal because there's so much more money to be made overall. This is possible mainly near transit [[metro), where the land value and demand to live in that particular spot is so high that the county can freely mandate all sorts of community benefits [[parks, affordable housing, new sidewalks or trails, new school buildings, etc.) and expect developers to simply say "ok" for the chance to charge all those $2000-$3500 per month rents or sell all those $750K condos.

Basically, if there's enough demand that developers want to build without any subsidy, then you can charge them some fraction of their expected profits for the right to build in the form of mandated affordable housing [[or other things). Again, Detroit is obviously nowhere near that point yet. But as demand rises, a city should gain leverage, not lose it.
Sure, which is why I specifically mentioned zoning exemptions as a way cities get affordable units. You are certainly correct that those exemptions become more valuable as land gets more expensive, while the cost of building an additional unit doesn't really go up much, so you can bargain for more affordable units in that situation. Of course, you need them more too.