Expect to pay a wide range for the sites; from $10 or so at National Forests to over $50 for private RV resort type parks and everything in between. Average for us is around upper 20's per night but we prefer state and national parks and have the senior pass. You can control food cost by whether you eat out or do your own cooking. Paying for tourist attractions can add a bunch or you can hike, fish, etc. You will use a lot of fuel when on the road but you can control that too to some extent. Compared to hotels and resorts and eating out 3/day you will save a lot if you don't count the cost of the RV.