That is indeed the Mormon belief and it is indeed incorrect. Quote me a source in the Christian bible for that please. God's grace is free and unconditional, you don't have to pre qualify.
What I mean is if I truly believe in God, good works will follow naturally. My life will change. I will want to please God-—and that over time I will put off the natural man. I do not believe that one can really believe in GOd and continue to be willfully selfish, cruel, etc.
The Bible says, “Faith without works is dead.” That is what I mean.