First of all, I don`t know what the current laws in Washington DC are, but alot of states are not allowing small business owners to register their home/ apartment to do business out of. 1. because you are in a residential area 2. Because of the Liability that the landlords face if one of your clients where to fall in front of the building. and 3. Because of the foot traffic.
And... although, most small business owners take the extra precaution to register their business, pay their taxes on time, and create new jobs for people, the government or should I say "City Officials" are getting more stricter than anything... I was in your same situation at one point, I went to my local City Registrar and tried to get a permit. They wouldn`t give me one because I was on a residential area. So what I did was I looked for a house on a business/residential area. Then I was able to register it because I had two businesses on both sides of my building and it was on a commercial area...
What I would suggest doing is, find a friend that has or wants to rent you some office space, even if you don`t work there... and... register your business under her address. It`s not the best thing to do, but at least you will be doing it legally.
Web Developer / Owner / Consultant
When starting your own business the need to "know-how" is greater than money!