1998 Holiday Rambler Vacationer? 13k Is it worth it?

Have you seen decent photos of it? Can you see if the license plate or inspection stickers are current? If not, how long has it been sitting?
At that mileage and price I can almost guarantee you it will have aged out its tires, that alone will run you another $2,500-$3,600
Before you get into the other stuff. If you really are limited to $13,000, plan accordingly.
At your price point, why not a trailer? Do you currently own a vehicle suitable for towing?