While you were poking around in some abandoned, ruined place that others of your people avoid, you comes across a hidden cache of ancient treasures, start with maximum starting gold for your class. (work with your DM to determine details)
In adulthood you have an encounter with an unusual person, who as far as you can tell, has no home or family. You offer to help in anyway you can. After accepting your hospitality the stranger vanishes leaving a note "Your kindness will be remembered".
the home town where they lived was destroyed, there was little loss of life. However, after the disaster passed, the area was rebuilt and has become more prosperous than ever before.