Is seeking an additional evening job considered unlawful (haram) and negatively impactful on young job seekers, given the existence of a respectable and rewarding morning job?

There is no harm in seeking additional work to increase one's wealth, as long as it is permissible and does not distract from religious obligations. Allah says: "There is no blame upon you for seeking bounty from your Lord," and "It is He who made the earth subservient to you, so walk among its regions and eat from His provision. And to Him is the resurrection." However, if the work is forbidden, or distracts from a religious obligation, or is sought for showing off and boasting, then it is blameworthy. The Prophet, peace and blessings be upon him, said: "If he went out striving for show and boasting, then he is in the path of Satan." And it is from the station of Ihsan (excellence) for a person to be content with what they have, and to leave work opportunities for those in need, and to dedicate themselves to the worship of Allah; for Allah says: "So when you have finished [your duties], then stand up [for worship]. And to your Lord direct your longing." And for His saying, peace and blessings be upon him, as he narrates from his Lord: "O son of Adam, devote yourself to My worship, I will fill your heart with richness and relieve your poverty. And if you do not, I will fill your heart with preoccupation and will not relieve your poverty."