@matt619 He's been sick and bedridden throughout his entire life, longing to be with friends, participate in activities, fall in love or even have a single glimpse of a normal life.
He can get money anytime, but school is something he will only be able to enjoy NOW, and nothing, not even a dragon (waifu) will prevent him from enjoying his school life.
Besides, he's so lacking in common sense he would most likely be scammed out of all of his money.