DCA 737 is still small and as a result there is very little open time for reserves. Expect a lot of short call assignments. Unless you just love the insides of airports, a crash pad will be necessary.
What few trips come into open time are typically non-commutable: very early shows and late finishes in DCA and BWI. Public transit is not 24/7 to all airports. The good news is that Uber is now able to pick up from DCA and IAD (BWI unknown), and there are many deadheads built into trips, allowing for commutable deviation.
Just my experience in the first month operating DCA 737 reserve.