I use this site (there are several similar)
Free Campgrounds for RVs
In small rural towns, I stay in City Park or Fairgrounds. (often they are free and some have hookups)
In a pinch... I use Hospitals, Funeral homes, Churches, farm yards.
I will go to a farm store about closing and meet someone who will often let me stay for free on their farm.
Typically I use Hospitality guest homes for travel ($10/ night worldwide). Many are farms and let you stay for free in RV. I have done this often on East coast States (even more often in New England).
Since I burn free cooking oil for fuel... my biggest expense is food (I usually get surplus veggies / fruit / dairy from Grocer discards). Just show up about 7AM and ask.