There are all sorts of places that allow overnight parking for RVs.
Cracker Barrel
Cabelas
Walmart
to name a few.
I have stayed at a truck stop but found it way too noisy. I travel to Florida from New York in the WINTER so there are no $40. night campgrounds OPEN.
We overnight in Walmart parking lots on our way to and from.
Please note - if you use facilities like these make sure you ask and park where they allow RVs to park.