Our congregation has just appointed two men in their mid-twenties as our treasurers. Is this scriptural? I always thought it should be older men. Our congregation also doesn't have elders or deacons.
Typically the physical needs of a congregation is handled by deacons, but the congregation where you are doesn't have any deacons. Yet, the needs still must be handled. Bills have to be paid and contributions have to be counted and deposited. The fact that the congregation asked two men to deal with the money shows someone was thinking. I know far too many congregations where only one man handles the money. Having two men is "providing honorable things, not only in the sight of the Lord, but also in the sight of men" (II Corinthians 8:21).
Since the congregation is doing the best it can without deacons or elders, and you can't apply the qualifications partially, there is no age requirements for someone who is helping a congregation until it matures enough to organize itself as God directed. As far as capability goes, accounting does not require age to be able to be done correctly.