Engine Light

I am looking at buying a 2011 Subaru Forester with just over 100,000 miles,
when I went to test drive the car the check engine light was on, the cruise
control was flashing, and the traction light was coming on. I mentioned my
concerns to the seller who said they had just turned on, and didn't think it was
a big deal. He took the car in to his father-in-law mechanic, and claims they're
off now, and had to with his wife having left the headlights on, and draining the
battery. Obviously I'm a little hesitant to purchase a car that could have
mechanical issues, I'm a young woman and this will be the first car I purchase
myself, and I am certainly no expert on this kind of matter. I'm wondering if
that's a plausible reason why that problem could have been happening, or if its
likely that those same lights will just turn on again, and indicating a larger
issue.