T37Solare made mention of Herrington Harbour. It has two facilities (north and south) but North is the larger one and has several independent vendors who have leased buildings over a long time frame. I'm not sure there is any available sheltered work space at this point in time, but I'm pretty certain you'd get the short end of the stick being the new guy there. You can call 800 297 1390 to talk with management.
Another possible choice is Pleasure Cove Marina near Baltimore. They are much more relaxed than Herrington but I'm uncertain about their availability for you. For a picture and more info see:
Pleasure Cove Marina | Pasadena, Maryland (MD) | Waterway Guide Marina Close-Up