Just a few tips:
Do not give them person information such as credit cards and bank account.
Try and understand the work being done by talking to the person. Ask "How will you perform the work? What will you be using?" ect.
Make sure the work being done isn't from a system that requires initiation, if the work does require initiation into a certain religion or system of magic, check around for their legitimacy in the community.
Talk with them, look for key words and hints at buying something further than the work being done, such as "a dark cloud over your head, more work needs to be done, get this item here for x amount of money to complete the work." This is a classic scam; a snow ball effect which could cost $100's dollars.
You've probably set your mind on what you want to do, which is fine. Just be safe when working with psychic readers, witches, or spiritual and conjure workers. There are probably a few websites that help with finding a legitimate worker, such as the AIRR, and organizations helping to stop fraud such as SAFE.
I wish you the best of luck!