The duty to earn relates to need and responsibility for dependants. Someone who must provide for essential personal needs or necessary household maintenance should pursue permissible means. This does not mean every person in every situation must hold a paid job.
بَعْدَ الْفَرِيضَةِ does not mean that work is lawful only after a prayer has been performed. The wording keeps central religious obligations in view while emphasizing the duty of necessary livelihood.
For example, someone responsible for a household’s maintenance may need an honest livelihood to fulfill others’ rights. The same circumstance should not be assumed for every person who is himself or herself dependent on others.