Hi- Baltimore is a bit far for nightly trips to DC. I think it is 45 minutes one way. Are you planning on having a car?
Do you definitely have to fly into BWI? I know sometimes it is cheaper but sometimes IAD (Dulles, in Northern Va) and DCA (in Arlington) are not much more $$$ and are a LOT more convenient. Have you compared flights using those airports?
The MARC train (train from BWI) has always taken me a long time.
Arlington is close to DC and it would be feasible to go into DC every night.