If you want out, go to your local bank or credit union and get a loan to cover the difference between what you can sell it for and what you owe. Then sell the sucker. You made the decision to finance a depreciating item over 20 years. You are stuck with it. If you have the financial means to pay, the bank is not going to just take the loss, they will file liens for the deficiency balance and will collect it from either you, or your estate. Even if you have to pay back a $50,000 loan, it will cost you less than paying for the RV, the storage, the insurance and the like. It sucks, but it is not anyone's fault but your own.
I would avoid any rental situation, like I would avoid the plague. The only thing worse than paying for a rig you are not using, is paying for a rig that someone has trashed beyond repair. I doubt there is great demand for 13 year old rental rigs, so the market would only be at the bottom budget end, not the best renters.