What is the ruling on going to a legitimate raqi who asks for money, and is it possible to be certain of the presence of envy or sorcery?

Legally permissible Ruqyah (definition) is allowed even for those who are not afflicted, and it is permissible for the reciter of Ruqyah to take a fee for it, as Abu Sa'id al-Khudri did. The reciter does not cure anyone; healing is in the hands of Allah alone. If no benefit is achieved, one can seek another reciter or consult psychiatrists.

Regarding what the reciter took: If the transaction was a lease (i.e., requesting the recitation without stipulating a cure), then he has the right to the fee. However, if he stipulated a cure, then it is considered a Ja'alah (a contract for a reward contingent on an outcome), and he is not entitled to anything unless the cure occurs.