I know this is a couple of months old and don't know how you've done in your search but with lots of experience living in DC as a liveaboard I'll give you my two cents worth. EZ Cruz and Tantallon are dumps and I won't recommend them to anyone. Tantallon rebuilt their docks but no services and a really, really horrible commute to get in and out of there at rush hour. If you check Deale, Md there are several there, Shipwright being the most resonable, and with the new Wilson Bridge express routes the communte to Quantico isn't bad. The Gangplank in DC is quite nice but you'll have to buy a boat already qualified as a liveaboard. The best bet to do that is to contact Joe at Gladys Marine
, he sells boats at the Gangplank and knows the ins and outs of getting in there.
If you get into the Gangplank you can leave an "old beater" of a car at the Springfield Metro station, walk the 1 and a 1/2 blocks to the metro, then take the metro to Springfield and have an easy drive to Quantico right down 95.
Any other questions PM me and I'll be glad to provide answers. I lived aboard in DC and Annapolis so know the ins and outs of the different marinas in the area.
If you are a sailor you definitely want to be on the Chesapeake, we had a 42 in Annapolis when the drive was horrible but the sailing was worth it. You have your priorities and need to adjust accordingly like we did.
Northern Virginia has a lot of rules against liveaboards and if you get caught as a "sneak aboard" you'll have to find another marina that day. Not worth the aggravation in my opinion. Also, Fort Washington
in DC is on Federal land and is not allowed to have live aboards, some managers have permitted them but when caught they got fired and the people got kicked out. So be careful of marinas on Federal land, the Gangplank is on Federal land but has some kind of clause in their contract
to allow it. Although DC has tried, and failed, to crack down on it.