Originally Posted by
choster
You'd need to get to Union Station in DC and from BWI or Penn Station in Baltimore, and that is the tricky part— Union Station is not in a residential area (and at the opposite end of city from Georgetown), so you'll need to walk, bike, bus, or Metro there. Penn Station, similarly, is not in downtown Baltimore, so you'll have an extra connection to make on that side.
There are residential areas within a few blocks of Union Station. Plenty of people live just east of the station. But OP was talking about living in Georgetown. From there, the easiest thing to do is the Circulator bus. I'm not sure how long that route takes.
And, while Penn Station is not quite downtown Baltimore, it's not very far and, depending on where one were going, could even be walkable.
I'd expect the biggest issue to be that the train schedules are more geared towards people coming to DC from Maryland, not vice versa.