A man down on his luck in an experimental welfare program where for a substantial lump sum determined by his family medical history, employment prospects, etc., he agrees to end his life at an age set out by the program. Population control, motivational experiment, etc. He doesn't know how he will be paid out, if / when that time comes. Maybe he gets 250k now, if he agrees to die in a decade. Up to him to make the best of it.

So he does soul searching, decides he doesn't want that deal. He loves his life, his friends, his family. He wants to take his chances. He buys a lottery ticket and wins. Feels immense relief at his choices, feels like he tested God and won. He doesn't need that shitty deal now, his choice to live has already paid off. He tells everyone. Tells his family it's all going to be okay. Dreams of what he will do with that money. Begins planning his life around it.

Then finds out the lottery was fixed, it was the system of payout to keep the money and the suicide or murder off the books in welfare program. I don't know what happens next.

There's your book, OP.