It depends on your level of knowledge and how much you're willing to pay. You may end up dumping more money into it than what's it worth just to get it running right again, and potentially chasing gremlins for the rest of the time you own the car. On the other hand, it may be a steal and could be something simple. I'd ask him what the car is doing and what leads him to blelieve its a "cylinder issue." Just do your homework and go from there. Ask him to take it to mechanic you know and see what the mechanic says. You have many options available.