If this is your bike, have it straightened, or continue to ride it as if the handling is OK

If it's one you're considering buying, take a pass. If a front end collision bent the fork, there's also the possibility that it buckled the frame. This is usually obvious by slight rippling under the down tube up at the head lug, but can't be seen either way in the photo. Anyway, there are enough great values in used bikes that you don't need to get involved with one that already has a repair bill attached.