Yeah, property taxes can kill you in a few states (Virginia for instance ...).

Besides the DC insurance on the car intself, which it sounds like you're not positive about (you might want to look into that ... you don't want to get on the hook for an Aurora if it were stolen!), is liability insurance ... I don't know what other coverages you have, but you might want to think about an umbrella policy if you plan on maintaining that "lifestyle" of automobile ownership ... I don't know what your other assets are, but if you're paying $650/month for a car, you're obviously not destitude, and if you were to get in an accident and injure someone, you could quickly go through the liability insurance I believe the car rental company is required to carry (typically the state's minimum, which is usually only like $50k). DC does not provide any liability coverage I believe, and you usually still have to count on your own for that (for instance I know off the top of my head we carry at least twice the required liability insurance on our policy).