Well, "weird characters"could very well mean GPU artifacting. This-card-can-boot-up doesn't mean its good-running-condition-for-gaming. I mean, hes blatantly telling you there is something wrong with it. Don't expect it to be something you can fix either. Even in good-working-order that video card isn't worth more than $50. You could ask for an image of what comes on the screen when he boots it up if you wanted to dig deeper, but why waste your time?