Back in my even poorer days I did my traveling by hitchhiking. Needless to say there was no budget for motels or campgrounds back then. I've slept in many public parks (be gone by dawn so the soccer moms don't see you and call the cops). Out here in the west there's often brush and/or trees alongside freeway on/off ramps that'll provide you with enough cover for a stealth camp site. A great place when it's raining is underneath freeway overpasses. Up near the "roof" of the overpass there's usually a nice flat area before it slopes down to the road below. Nice and dry.
Even if you get "caught" usually the worse that happens is you'll be told to leave. So fine, head to the next jurisdiction and find a new camp.
Canis meus id comedit.