Simony is the buying or selling of God’s grace. Objectively a mortal sin.
It is named for the magician named Simon who heard the disciples talking in tongues and raising the dead, etc. He went to Peter with money and said “Let me have this power too.” Peter replied “Your money perish with you for thinking God’s gift can be bought! Turn away from this great wickedness and pray.” etc. etc.
It would be simony if one were paying the priest for sacramental absolution, for example, or imposing Holy Orders. But paying a priest a stipend to say Mass for a dead relative would NOT be simony. Why? Because you are giving him a small gift for a SERVICE and not trying to bribe your own way into heaven. You are giving him a donation for what he needs to live. ANd of course the money has absolutely no effect on how soon a person is sprung out of purgatory. As long as everyone understands this I think there’ll be no problems
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