My husband has a friend who with out our permission left his Rv in the back lot of our property and over the past 5 years has has so many excuses as to why he will not remove the Rv.

How can we remove the RV at the cost of this person.

You could call the police and ask them to have it towed away to impound. However I would first let him know in writing that this is what you and your husband plan to do.