C50 Priority
As for why he accepted disciples under the age of 18, it was because people over the age of 18 weren't strong in terms of flexibility. Since he was going to be Master Ling Tian's disciple, even if it was just to fulfill Tong'er's wish, he wouldn't let it go.
Otherwise, with Master Ling Tian's fame, he would be willing to just grab a few people to be disciples.
"Snowy