My first "modern" road bike, which I also found on CL, was that same bike. Mine had been upgraded to full 5600 (Shimano 105 group- two "steps" higher than Sora) except brake calipers. I paid $400 for mine. Sora components are near the bottom of what's acceptable in terms of performance, durability and serviceability.

Only you can decide whether or not this would be a good value for you. Personally, I'd pass and try to find something with a 105/tiagra mix, maybe, for roughly the same asking price. Or offer $400 and see what the seller says....

Good luck.