i don't think that a high schooler can get rich like that, he's probably adopted by a rich family or his father after his mother got reported or something similar
why do i always forget that in mangas high schoolers are able to get rich just like that by themselves XD ?
but someone said in the beginning he's a heir of big corporation. but i don't remember anything about his family being revealed in the raws but i might be wrong (except for his mom). to many webtoons in a short time (⊙…⊙ )
Maybe his mother was a mistress of some rich guy. Smt happen to her, the rich father got him back.
Huhuhu! These poor children! ╥﹏╥
On another note, is this part of why Woojin changed so much and got rich? So that he won't be empty anymore and save Taemin?