We currently camphost at a Virginia State Park and a Maryland State Park. On the applications, it asks about what type of animals and how many you will have. They are accepted in both of these states.
At the park in Maryland, Point Lookout, they had 6 different campgrounds and we were assigned to a "non-pet" campground, but we parked our rig in one of the pet friendly campgrounds, which was adjacent to it. It was no problem, we just had to walk an extra 100 yards to get to the campground. This park is located south of Annapolis by about 75 miles on the point (hence the name) where the Potomac River runs into the Chesapeake Bay. It is a fisherman's paradise.
Point Lookout is always looking for hosts and it is a wonderful place to host. They appreciate you and do what they can to help you, help them. They really like hosts to stay for several months, but will accept a month long term. The ranger in charge of hosts is Jonas Williams and you can contact him or you can contact Melissa Boyle, Assistant Park Manager at 301-872-5688.