How the Akatsuki members turned all "missing-nin's"?
Missing-nins are not shinobi that got exiled from home. That does not happen.

Missing-nins always are shinobi who went rouge and left their villages willingly.

No village would want a shinobi of theirs going away and possibly to some other village spilling all their secrets? Especially not very powerful shinobi who were probably high in the ranks in their respective villages.