We're in the process of buying our first RV to go full-time in and are located in Pennsylvania where we will be remaining for at least the next year. We want to travel around after that, but will continue to be focused on the east coast. The thing is that I've already road tripped around most of the US, and find the Georgia to Maine corridor to be by far the most beautiful part of the country. This is personal taste, obviously, but I don't see myself ever leaving the east for long.
There are definitely lots of places where you can boondock for free or at least with a very low-cost permit in PA too. We have tons of state parks and state forests. I did notice the state parks don't allow camping this time of year, though (I think they only issue permits April-October).
Also, this is just a thought I had, but you should be able to boondock for free in a van or even small RV at any of the parking areas for the Appalachian Trail. The trail is "open" 24/7/365 and thus so are the parking areas. There are detailed maps of the trail online which also show most of the parking areas. You'd obviously want to exercise judgement and not choose a parking area that's literally in someone's backyard (due to the right-aways of the trail this is a genuine possibility--one of the parking areas I use is like this) or so small you're in the way, but vehicles are regularly left parked for multiple days at the larger parking areas so I doubt anyone would mind.
ETA: I'm referring above to the parts of the trail that are NOT in state parks or forests or other "public land" areas. In those parts you're expected to obey the park/forest rules and they can be really annoying.