best bet is to visit the DC Bar small business clinic…free legal advice for aspiring and existing small business owners. http://www.dcbar.org/for_the_public/programs_and_services/ced_project/events.cfm
Honestly, I bet a lot of people just operate stuff like this out of their basements without getting permits, since it’s such a hassle to deal with DCRA and other agencies. Kudos to you for trying to do the right thing–it will likely be a gigantic headache (paying taxes, licensing, etc.) but at least you won’t have to worry about being caught.