How do I know I have enough room to back down driveway?

Where we store our RV for right now is a normal sized street.
We have a 42’ fifth wheel with a 2016 Ram Crew Cab short bed. Yes it has the slider but we never use it.
So basically I drew it out on the photos to give you an idea of how we do it.
I drove past the driveway on the wrong side of the road, then begin to back in.
Usually I have to pull forward just to realign myself so I pull up to my bumper on neighbors drive across the street.
Then a straight shot back in.