Ruling on taking a percentage in exchange for clearing financial rights

Question:
A man, who is a lawyer in one of the countries, agreed with a group that he would clear their rights with the state. So when he exerted himself, made an effort, and spent money from his own pocket on this matter, the matter became easy and they received their rights. He had stipulated that they give him a percentage of twenty percent of these rights, and they agreed to that. He said, "I looked into the matter and found that perhaps, had I not made this effort, their rights would have reached them anyway. Is it permissible for him to take this percentage?"

Answer:
If they hired him to clear their rights, there is nothing wrong with it.
Q: They hired him for a percentage.
The Shaykh: If he clears their rights, there is no contradiction.
Q: He says that the rights were cleared easily; it was possible for them to be cleared without him, but after he made an effort and spent money?
The Shaykh: There is no harm.