Getting a reading done and doing a spiritual service are two different things. If you are "employing" a psychic reader for their services, you are paying for their time and you are asking them to do a service for you of a one on one reading. You always have the option of NOT asking for that service. If someone is giving you a service, you pay for it.
I can even see giving a donation to a church for their time in coming to bless a home or deal with an unruly entity. I've done it. But that has always been an offering, not a charge, and the people I've asked to do it came with credentials.
My concern with shop owners is anyone can claim to have knowledge. If you are going to employ someone, ask for verifiable references. Who have they done this for before? Who can you verify with that they were effective? Here's a story for you. I personally know two nitwits who decided they were ghost hunters and could "clear" a house. They advertised themselves as such. They had never in their lives done anything in the paranormal. Ever. They had no clue and walked in with a book trying to fake it. They not only stirred up the place, they set something loose that took a legit intervention to settle down. Vet anyone coming in your door. Anyone can claim anything.