So if a man is a Jesus only believer, and a woman is a believer in the Trinity, but they are both saved, and they both live for God and want to get married, is that a reason not to get married? Could the trinitarian woman stilll go to the man's church and worship Jesus? Or would this be too much conflict in the marriage?
I'm not an expert on the Jesus-only (Oneness Pentecostal) beliefs, but here's what I see. In John 1:1, it says that "In the beginning was the Word and the Word was with God and the Word was God". Also, the Lord's prayer found in Matthew 6:9 begins, "Our Father, who art in heaven...." And in Luke 23:46 "Father, into your hands I commend my spirit." In all of these verses, it's clear that Jesus and the Father are two separate and distinct persons. To deny these verses is to deny the truth and teachings of the bible.
In 1 Timothy 2:5, the bible states that there is one mediator between God and man and that is Christ Jesus. If a person is accused of commiting a crime and goes only to a mediator, but not to the judge himself, he walks away no different than he came. It's the mediator's job to plead the case to the judge, who then has the final job of assigning guilt or innocence. So, if a person believes that the Father (final judge)doesn't even exist, that person hasn't been pardoned.
Only God can know our hearts, but in my opinion, the man who does not believe that the Father (final judge) even exists, and the woman who believes in the trinity and the face-value teachings of the bible, are not on level ground, spiritually.
This is just my opinion, based on the teachings of the bible, but if this were my situation, I would be concerned for my spouse's salvation and eternity.