Originally Posted by JoeT
Some states, Texas is one, allow overnight parking in rest areas.
Here's a link to free or low cost RV Parking. Free Campgrounds for RVs
All states allow you to sleep for a few hours at a rest stop. You're just not supposed to set up camp, (slides, chairs, awning, grill), and stay overnight.
That being said, rest stop RVer's are very easy targets for thieves. Especially, if they observe that you have been sleeping.