Suppose if I had a brother that doesn't pray, and no matter how much you advice he won't pray, but he cares about money so if you give him money he will start praying, and if I kept giving him until he gets used to it and Allah guides him. Is this permissible?
May Allah forgive me if I am wrong, but I think that it is permissible. It is permitted to punish kids above ten years old in order to motivate them to pray. If punishing is permitted then positive incentives should also be permitted as it achieves the same goal.
Yes, it's permissible. You can ask him to pray with concentration and attention and slow. Slowly he'll start praying without money.