I have never seen anything that suggests a minimum measurement for bedroom size. Bedroom size usually means the number of bedrooms in the home or apartment that the housing authority is willing to pay for. I have experience in Chicago, NYC, and Atlanta with section 8. Bedrooms must have closet and window, but NYC has lofts too. The housing inspectors will go with local custom as far as actual room size. A 3 bedroom of 900sqft is usually not as valuable as 1800sqft. Just know that they inspect hundreds or thousand of props per year. Do not turn the walk in closet into a bedroom.... It happens often here in GA (smile). Also some people want a bonus room that they will use as a bedroom later, but housing does not pay extra.