Although a 60-year-old guy dating an 18-year-old girl is not violating any laws, I don't believe it is practical, and most importantly, I don't think it is healthy. The guy should know that the girl is not mature enough to really think of the repercussions of being in a relationship with a man old enough to be her grandfather. There will be a lot of issues concerning the age difference, like mental capabilities and behavioral differences. This huge age gap in a relationship is really difficult to handle and does not work out very well most of the time. I don't think it is very healthy to invest in such a relationship.