Jain scriptures do not fix a numeric “minimum age” (like 18, 50, 60, etc.) for taking the vow of sallekhanā (santhārā).

Instead, they lay down conditions, mainly:

1. End-of-life situation

- Very old age (vṛddhāvasthā) - Or incurable / terminal disease - Or extreme situations like famine, where living on normally would involve more himsā.

1. Spiritual and mental maturity

- Stable, peaceful mind (no depression, hopelessness, or desire to escape problems). - Strong faith, long practice of vows and ātmā-chintan.

1. Worldly responsibilities mostly completed

- For a householder, major duties toward family should be fulfilled.

1. Under guidance of a competent Guru

- Achārya / muni / sādhvī / āryikā (or in their paramparā) decides if the person is truly eligible. - It must never be done independently, especially not by youth.

So practically:

• Children and young people are not considered eligible.
• Most authentic cases are in advanced age (often 70+), or at any age only if there is a clear terminal illness and proper spiritual qualification.
• Both Śvetāmbara and Digambara traditions agree on these conditions; exact community guidelines (like “after 60/65”) can differ by saṅgh, but those are internal rules, not scriptural numbers.

In short: There is no fixed minimum age in texts, but sallekhanā is only for those at the natural end of life (or truly terminal illness), spiritually mature, with duties largely completed, and always under Guru’s direct guidance—not for the young or for solving worldly problems.

You can read more on Santhārā/Sallekhanā here