One of my colleagues from college married a former student of his

Give it 10 years before you decide how you feel about it. A childhood/HS friend of mine became a teacher and ended up marrying one of his students. He wasn't 12 years older but he was at least 24 or 25 and she was 18. They did everything right in terms of not dating until she was of age and out of his classroom. They've been married 15 years now and have a couple of kids. So while it was a tad strange at first, it worked for them.