JLPT N3. Used in both writing and conversation.
さえ is a versatile particle that is used most commonly with the affirmative conditional to place emphasis on one thing, e.g. If only I had time, I could travel the world. In this case, さえ takes the place of the object particle.
さえ [VERB: ～ば]
You will often see it used the verb “to exist”: さえあれば.
If I just had half a chance I think I could make it work.
If I only had time I could realize some many plans.
If I just had money I could spent every day freely without worrying about tomorrow.
さえ can also take the same role asでも when used without the conditional. The meaning is identical, but さえ has a stronger emphasis.
His phone number? I don’t even know whereabouts he’s living now.
My foot hurts—even walking is impossible.
さえ can also be appended to the verb stem, but this structure is rarely used either in conversation or in writing.
[VERB: STEM] さえ すれば
If you could just agree to this point, then as for the rest I think we can find a reasonable compromise.