Accessory dwellings are rentable units inside another home, like a basement apartment or an upper floor with a separate entrance. These are common in DC, but illegal in Arlington. What’s Up Arlington reports an intiative underway to change this law.
I don’t know about Arlington’s motive specifically, but many suburban jurisdictions originally made them illegal to keep housing prices high and, intentionally or not, prevent poorer and minority people from living in their towns. With housing prices now so high for everyone, there’s political will to change the law. There’s a public meeting Monday to discuss the proposed changes.