Identifying small property landlords in PUMS

Hi -

I was looking at this Urban Institute blog post:

I was interested in reproducing it using PUMS data for Cambridge, MA, where we have many small building landlords. As I started working on it, I quickly came to the conclusion that they must be conflating "landlords" with records for property owners. Does anyone know how to identify landlords in the ACS data? I think you could look for housing records for units that are owned, but that doesn't tell you if they own the whole building. You could look for records where the condo fee is $0, but that is not a guarantee. I could not find a way to contact the authors, but it seems suspicious that they have a chart showing race/ethnicity by building size for landlords - how many 50+ unit buildings are owned by a single owner that lives in the building?

If it is true that there are just errors in this analysis, does anyone have ideas on how to look at demographics of owner-occupied small multifamily buildings, ideally at the city level?