Hello =) Yeah ''Errand Boy'' means something like 'Garoto de recados'' ou ''garoto que faz entregas''. This is basically what 'errand' means, delivering things to someone, usually for money.
Some exemples from my dictionary.
Definition: A short trip you make to do something, such as buying or delivering things in the neighborhood:
''He would clean, do errands, and babysit for their 7-year-old daughter.''
''I’ve got to run a few errands (= do errands) and then stop by my mother’s.''
''He used to be an errand boy in the free time''