There are two important departments you'll need to contact about basic information to get started. The fist one is the DC Department of Regulatory Affairs (DCRA) to obtain a license. http://dcra.dc.gov/DC/DCRA
Then you will need to contact the DC Office of Zoning, I've attached this site as well for you (http://dcoz.dc.gov/info/map.shtm). Please call me if you have any questions.
I know of some great places in DC that may be a good fit for your business needs, and would love to discuss it further with you.
Best of luck!
KANGAL REAL ESTATE
(202) 674-1671 cell
(703) 888-1463 office
There are several great bed and breakfast through out Washington DC neighborhoods. One being in the Bloomingdale section of Ledroit Park. I'm sure with the correct license and permits etc... you will be able to do the same.
We find that issues of this nature are often a "toss up" depending on your particuar locality. Our recommendation is to defer this to the local zoning governance and be on the safe side.