This paper seeks to test the claim commonly put forward by preservation advocates that older housing is less expensive than newer housing and that this warrants policy intervention expanding the preservation of old buildings, by employing regression analysis, spatial data analysis, and visual surveying to elucidate the relationship between residential housing units’ decades of construction and median rent cost across Cook County, Illinois. This paper finds that, across Cook County, newer housing is typically more expensive than older housing, yet with significant variation in this relationship between census tracts. This paper also finds that, although density of housing is important in informing this relationship, much older housing is also intrinsically more affordable than newer housing when accounting for upkeep and density. Accordingly, this paper recommends the expanded preservation of older housing of middle densities and wider permitting of the construction of accessory dwelling units on parcels with historic single-family houses.