It's an interesting thing, this question of "what are the conditions of salvation?" Is there just one—faith? Or perhaps two—repentance and faith? Scripture often mentions them together. But they are also stated singly as the requirement. This is confusing and seems misleading. Are they somehow integrated so they resolve into a single complex act? And what about the many other conditions of salvation—be born again, become as a little child, hate your mother and father, forgive your brother from the heart, love your enemies, get baptized, don't look back, take up your cross, follow Him, endure till the end? Can these all resolve into the two, or one?
The way we are taught to approach scripture—plucking verses out of their context to form lessons or sermons around, or compiling lists of verses supporting a view—does not serve us well in getting to scripture's answer to this question.
I believe Romans answers this in a lengthy, systematic theology style, that few will allow to speak as it as written—as fifteen chapters on the subject of how salvation works.
Of the four accounts of the gospel, I believe John alone is crafted toward the end of explaining what the gospel is and how it works, and it provides an eighteen verse prologue as a key to keep us on the track of meaning through the whole story.
The book of First John is the most concise and focused work on explaining the "how" of the gospel. But it is difficult to digest because it is written in such a way that it must be taken as a whole to discern the many parts. This may require reading through it dozens, or even hundreds of times, until our preconceptions are all shaved away and the meaning forms a unit instead of a bunch of disjointed aphorisms. This is because it presents the gospel as a story, true in history, in which all of the parts have meaning in the context of the whole drama. Unfortunately, First John is usually relegated to the junk pile as a letter with a message about a gnostic heresy from the first century—a historical footnote of deprecated relevance. This is entirely false!
Now I'll tell you what I think.
When asked, "What shall we do, so that we may work the works of God?" Jesus answered, "This is the work of God, that you believe in Him whom He has sent." (John 6:28c-29).
In First John we read that the one who has faith has overcome the world. That means we stop sinning and start loving God and our brother. We also read there that we love because He first loved us. So I think that when we consider the love of God expressed through Jesus' suffering and death on the cross for us, if we put our trust in His love for us, our hearts are transformed from selfish to loving, and we begin to love and obey. In this way, and this way only, as part of the whole story of all that Jesus said and did while on this earth in the flesh, faith becomes the single condition of salvation that includes all of the others and sets them in their meaningful relationships to each other.
"And we know that the Son of God has come, and has given us understanding so that we may know Him who is true…"