When we went to Maine the 2nd time, we stayed in Old Orchard Beach at Ne're Family Campground, which was right in town. We could walk downtown without taking the truck. The lobster pound was right across the street. Downtown was 3 blocks away. It was basic with a small pool, wifi, bath house with showers, electric, water and sewer. No other amenities, but about half the price of the other "resorts".
We checked out the southern section (Portland, Freeport, OOB) for 5 days, and then we headed on up to Bar Harbor and checked out Acadia NP and surrounding area for another 5 days. We stayed at Narrows 2.