There is a lot here.
First, get confirmation of the VIN. In my years of dealing with strange vehicles, many have turn up to be reported stolen or totaled. But, many were and the state's records were never properly resolved. (This can also be a great hammer to get the price down if you are sure that the vehicle is not "hot" and is registerable.)
Second, most non-dog campgrounds will say so in their website. There is a problem though, many have a two dog maximum or a total dog weight limit. While this is rare, a call will make it clear.
Lastly, If it is a Motorhome (you do not say), be aware that at 22years, all the rubber parts are aged out. Check the DOT-Date codes of all the tires. Seven years is not good and ten is asking for trouble. If they are 19.5 or larger, they are not cheap to replace. Not just the tires, but the hoses and belts as well. And, the coolant and brake fluid are also over age.
There is no reason that an older coach can't be reliable. Ours just finished a 4376 mile excursion and we broke a drawer slide.
Matt