Once upon a time, when “MF” really had no other connonation, it was fine to abbreviate “Multi-Family” as “MF.”
However, as real estate get both “younger” and more online, I suspect that “MF” is increasingly associated with another, not-so-nice definition.
So, here’s my advice to MLS: time to retire “MF,” and substitute “Duplex,” “Triplex,” and “4+ units.”