There is some good information from DCRA at rentmydcbasement[dot]wordpress[dot]com.
The R-4 and R-5 zoning overlays allow basement conversions by right (I think; I am not a lawyer). Otherwise you might have to the BZA to get a variance, with open comment period, letters from your neighbors, etc. etc. There is a link to the zoning overlay map at the DCOZ web site.
As far as being separately metered, it is not required but you might be adding service from PEPCO anyway if you go through the whole CofO route. At which point you might as well get separately metered. I would guess the cost at $5-7k if service is being added. But I am not an electrician either.