I sometimes boondock at county parks. Some of them are quite undeveloped and only sport pit toilets and a water pump for $10 a night and that is based on the honor system, you fill out an envelope put $10 in, and slip it into a locked box. Once a week a park maintenance guy empties the box, replaces the toilet paper, and leaves. Some of the sites are so huge you could easily park 2-3 trailers plus vehicles and many are literally water front property on beautiful lakes or rivers.
Last year we stayed at a nice place that had water, sewer, electric, and cable TV hook-up. The site was large enough to also park my boat, 2 vehicles, and plenty of room to spare including trees surrounding for privacy from neighbors. It was about $250 for a week but well worth it. If you google boondocking campsites you will find a lot of opportunities.