Currently, our budget is thus:
Campgrounds: $750/mo.
Fuel: $1000/mo.
Food: $700/mo.
Propane:$50/mo.
Miscellaneous: $400/mo.
Maintenance/repairs: $250/mo.
For a total of $3150/mo. This does not include health, cell phones, insurance.
In January, we spent $3014 and went over in food and fuel but were under in maintenance.
In February, we spent $2394 (so far) and went over for propane, under for every other category.
In January we moved a lot - repositioned and were in FL so campground fees were higher. In February we moved less and campground fees are much lower.
The previous 12 months were somewhere between these two depending on how much we moved and what part of the country we were in.
So, for us, full-timing costs somewhere between $2K and $3.5K per month. If we feel we are overspending, we trim back on eating out. If we have stuff left over, we do something fun like buy a kayak. It all evens out in the end...