Louise,
I can speak from both sides of the DC fence - grew up in Baltimore as a Marylander and am now a Virginian. No offense to the MD guys, but I never knew about general aviation until I moved to Virginia. There just aren't enough small airports in MD. Gaithersburg, MD is indeed has a wonderful airport, but the ADIZ makes getting in and out a real pain. Same for Leesburg, VA. Same for Manassas, VA. You could make a case for living in Gaithersburg (DC commute is do-able) or north of that and keeping the RV at Frederick, MD.
NoVA is not that much more expensive than MD. And I disagree, traffic isn't any better in MD, although I will agree that no matter what you are going to love the area for all that it has to offer and hate it for that very same reason - everyone else realizes that, lives here and traffic is just otherworldly. Frankly, if I had my druthers, I'd rather be living in Carlsbad.
Back to NoVA vs. MD. Like my esteemd friend, Richard Bibb now a newly minted Texan, I am also a Warrenton pilot. Either Warrenton (W66) or Culpeper (CJR) are the best local airports for sport aviation - lots of RV and other experimental and classic aviation types to hang out with and go flying en masse with. Shannon (EZF)in Fredericksburg isn't bad either. Although I am a W66 pilot, CJR is actually a more interesting airport. You'll see rare planes there that you won't see anywhere else. More Stearmans and Waco's than you can count, T-6's, Staggerwing, Swifts, the list goes on. Unfortunately CJR is a bit far to drive, but many folks do it. W66 has an incredibly bad FBO right now, so things are a bit ugly politically.
Cost of a hangar in our area is indeed in the 350-400 range if you have a NEW hangar. I have an old W66 county hangar - cost is 251/month. Your best bet is to find a high wing in a new hangar and buddy up like you mentioned. Or find someone with a Pitts to share. Cost would be closer to 200 to share.
Don't sell the RV, you will regret it. Much beautiful stuff to see just west of the ADIZ. Shenandoah valley, Atlantic Ocean, Chesapeake Bay, and LOADS of airports in western and southern VA to visit. MD only has this on the Eastern Shore, and well, we fly there all the time.
Good luck,
Rob