It's worth about $850.00. The Honda looking front blinkers look like they came off a "Trail 90". The fenders look after market too (along with the D&D pipe), but the black tape on the seat is a bonus. All the things I just listed are easy fixes. The fenders are probably better than stock, don't worry about the blinkers, tree bark will take those right off. Seat skins are easy to find and relatively cheap (as long as the seat foam is o.k.). Other than that it, looks like it was "rode hard and put up wet". If you can get the owner to fire it up, listen for cam slop and/or piston slap. Also, try to lift up the fork boots and check for blown seals. Sit on it first and compress the forks a couple times and also do the rear shock (it's easier, no boot). Also ask him if he re-jetted the carb for the pipe. See if you can get a look at the air cleaner, but not so much for dirt, but for rot.
Don't mean to "dog it out", but knowing what I've done to "Dual Purpose" bikes, I pretty much have an idea of what to look for. But even if you paid the asking price, a guy could still get his moneys' worth in fun out of it. Plus it would make a "back-up" commuter bike. I'd buy it.