This horse is older...21. He is a quarter horse arabian mix. I can see if I can post some pics. His swayback isn't TOO horrible though.
If he's already older then his swayback is only going to get worse and more uncomfortable so I would say to just avoid him.
I know you've been looking for a while and it sucks when you think the right anything, animal or not, and have to pass but you're just going to end up heartbroken if you get him and you can't ride him! Or you might get lucky and be able to ride him for a while but it's definitely a risk and it will eventually get worse.
I would say to just pass and try to find another horse.
It's hard to not go for the first possible fit but he might be a problem later.
OR.
If you really love him you could always get him as a companion for another horse, since horses need friends, and/or maybe just do light work with him