According to Biblical Unitarians, what is the essential belief about Jesus in order to be saved?

There is no need to define salvation - that is a given Biblical standard and requires no artificial additions to be a better salvation as contrived by a trinitarian insistence on trinity belief to be saved.

And this is eternal life, that they know you, the only true God, and Jesus Christ whom you have sent. John 17:3

Salvation is to be saved from death - the death of this age due to sin which all have become guilty of since Adam. Eternal life is the essence of this salvation - Jesus has become the first recipient and is the firstfruit of all creation Col 1. (1 Pet 3:18)

Jesus the human.

What Jesus taught about himself, what the bible teaches about Jesus is dependent on one truth - he is who he said he was. What various other sources teach about Jesus is not analogous to the Biblical record.

Jesus loved, was obedient until death, he trusted his God and overcome all evil - the instigator of evil, the devil.

He did all this not by being God, but by not being God. Simply because we are told that the very essential issue of trust is to believe that he came in the flesh.

For many deceivers have gone out into the world, those who do not confess the coming of Jesus Christ in the flesh. Such a one is the deceiver and the antichrist. 2John 1:7

If Jesus came in the flesh as required and was the 'man' he said he was (John 8:40). Then if he is also made equal to God, as God is God, we are not believers of this fundamental truth which Jesus provided.

Jesus answered, “I am the way and the truth and the life. No one comes to the Father except through me. John 14:6

"coming in the flesh" is not also, coming as God - as tradition insists he is based on an unbiblical incarnation idea. 'God becoming a man', is to be read nowhere in Scripture but is based on the imaginative invention of the church fathers who devised another Jesus who is not only flesh.

By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God; 3 and every spirit that does not confess Jesus is not from God; this is the spirit of the antichrist 1John 4:2

Jesus' offer of salvation is dependent on us believing WHO he is according to the warnings we are given. Or, apparently, we are trusting in an antichrist. Being 'made like us' is an irrational idea if he is also God.

Therefore he had to be made like his brothers in every respect, so that he might become a merciful and faithful high priest in the service of God, to make propitiation for the sins of the people. Heb 2:17

The popular interpretation of Phil 2:6 'emptied Himself' which allegedly impose on Jesus that he 'put aside his Godness' is without merit and eisegetical. As we are told repeatedly, Jesus is the image of God, the form of God, the representative of God. How can he be so if he put it aside? God becoming not God so he could be tempted and die is simply part of the 'mystery' devised by giving Jesus two natures - another idea without Biblical merit.

Jesus the overcomer.

Jesus said he had "overcome the world" (John 16:33) The only way he could do that is by resisting temptation as we all experience, against the evil we all experience by the power of God in him as we have a small deposit, by being a man totally dependent on his God and the reshaping of his differing will to align with God's will for him. Does God have two opposing wills? (making Jesus God produces this paradox)

Jesus had to choose God’s will against his own while continually resisting temptation. If Jesus was secretly God (and disingenuously so, because he only said he was a man) this would be an entirely farcical choice. If he was also God, this whole essential matter of overcoming would be of no consequence. What does he overcome is he is beyond sin as a God/man would be? Can God sin? If He (or Jesus) cannot be tempted to sin, then there is no temptation as we are told.

Salvation requires works to confirm our faith. Jesus had all the works to confirm his faith and trust. If there are no works, there is no faith - it is dead. Can salvation come to that person who trusts in a God/man who didn't really need to overcome anything, whose faith accounted for nothing but a show in a human manifestation of a Son who didn't really die, who could not die?

What is the salvation that Jesus offered? Eternal life.

Truly, truly, I say to you, the one who hears my word, and believes Him who sent me, has eternal life, and does not come into judgment, but has passed out of death into life. John 5:24

How is it possible? Because he died and God raised him.

That if you confess with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved. Rom 10:9

We either take the bible as it reads or we don't. Some say these words attack the trinity or the divinity of Jesus. They do neither. There is no need to justify the Bible to cater to a creedal construct. We are asked to accept the word Jesus and his Apostles provided, give thanks for the fleshly life he offered, and worship his God who raised him - plus nothing else!

Therefore, let all Israel know with certainty that God has made this Jesus, whom you crucified, both Lord and Christ!” Acts 2:36

How (and when) is Jesus made the Christ? Only after his death. Sure he IS the Messiah (Luke 2), but would this remain true if he did not die? Would he be the Messiah if he sinned? Heb 5:7

If Jesus is 100% flesh and precisely nothing else, then he can be the one the bible teaches us about, the man without sin - the saviour of all. If we make him God or eternal or divine as God is, then he is no longer mortal flesh like us - no longer the last Adam (human). These are the facts scripture presents and that is the foundation for salvation in his name.

If we choose to believe in another Jesus the bible does not teach, we have inadvertently formed another salvation - by our own words and constructs, not the words Jesus uttered, and the Apostles affirmed and taught.

Which Jesus is the way to the Father? Is it the Biblical Jesus, or the one devised from extra-biblical sources?

Jesus said to him, “I am the way, and the truth, and the life. No one comes to the Father except through me. John 14:6

Clearly, one single answer cannot cover all objections raised by traditional creedal adherents, but this offers a Biblical premise based on the man Jesus, who is not God by any stretch of an honest and thorough biblical study. Further material from https://www.biblicalunitarian.com/videos/do-you-have-to-believe-in-the-trinity-to-be-saved and other related text pages.