From what I've read over the past 20 years on RV Forums, people who sell their RVs using a consignment dealer have a love hate relationship. Some have been happy and felt it was worth it. Others were very unhappy with the experience.
I'd say if it was in excellent condition a consignment dealer is the way to go. With it being in fair condition, I'm guessing the price will be so low you'll see little or no profit if the dealer sells it.
One thing for sure is to get the dealer to provide a written marketing plan; what are they going to do to sell the unit.
I know your MIL probably could use the money if the unit sells but you may consider donating it.
Or advertise it in the current park, maybe someone has been admiring it and wants to move up from what they have.
