41.1% of land area is single-family only. Mixed-use, non-single-family + planned development is 33.8% of land area. The majority of residential land area in Chicago is zoned single-family only.
That's possible, but not a given. Unfortunately, it would be complicated to calculate (and perhaps not even possible unless Chicago's GIS system has good data for how many housing units are in those Planned Developments).
Even then, Chicago is probably close to a best-case scenario, not representative of the norm.
Take households from census data, divide by number of buildings. If the number is greater than 2 you're wrong, less, you're right. But I don't know if that data is available