Depending on where you live, there may be areas close to you that are "unclaimable" and therefore "free" for you to use (annoying parking fees aside). The Auburn State Recreation Area is one of those (and one that I have frequented). This includes most of the North Fork of the American River, and part of the Middle Fork American. Past the Recreation area on the North Fork is considered "Wild and Scenic" and is also unclaimable (for the most part). If you are within the boundaries of a State Park like the ASRA, you shouldn't have to worry about jumping someone's claim. However, it's always best to double-check any specific area that you're thinking about trying out. Good luck!