levite

No particular career or profession is any more noble than the people doing it.

The mark of true nobility, IMO, is to cherish the wellbeing of others and work for it, to foster justice and compassion and lovingkindness wherever possible, and to seek as much and as powerfully as possible for those around oneself to be empowered and improved by education, opportunities, and freedom; and not to seek for oneself either glory, or fame, or riches, nor to be mired and distracted by gross materialism, intolerance and hatred, or egotistical self-service.

That said, it is certainly true that one cannot, of one's own accord and decision, suddenly become noble. By living one's life with integrity, grace, and an eye toward the problems of others, one may perhaps be called noble by others. But nobility is a thing conferred, and cannot be purchased, or taken by force, or acquired by self-acclamation.

__________________
Dull sublunary lovers love,
Whose soul is sense, cannot admit
Absence, because it doth remove
That thing which elemented it.

(From "A Valediction: Forbidding Mourning" by John Donne)