Pass him by. Intermediate means just that, she's not saying it but to me that says he is either very forward (since she contradicts herself when she says he will go anywhere in a trail ride) for the fact he led the trail ride. Trust me a horse that makes you battle to keep them in a trail line makes for a very tiring ride. The reason she is only getting offers for $500 is the fact he is not registered and he needs an intermediate rider, in the area we live that is about the value of a non registered horse unless they have some fantastic training. The "3" rating is probably leaning a bit low, I would see if you could contact the previous owner who didn't want to ride him. That lady sounds like a beginner who got rid of him since he was too much to handle.
The other factor is I don't see anywhere his age is listed and I love to see what bloodlines a horse has as in walkers some are bred to be forward and some are bred to be good trail mounts. For a beginner I think the more you can find out about their pedigree the more you can tell what temperament you may be dealing with.
Horse prices really haven't gone up much at least in our area so I would just take my time and keep looking since I feel for 1300 you should be able to find a nice calm trustworthy trail horse that will give a beginner the confidence they need to enjoy the hobby rather than having an animal that will scare them off. If you don't have fun you soon learn to hate it.
Good luck in your search.
A woman can NEVER have too many horses.....