The spell, Create Homunculus, specifies the following:
You can have only one homunculus at a time. If you cast this spell while your homunculus lives, the spell fails.
However, the Homunculus Servant infusion of the Artificer lists no such restriction. Does that mean they can exist concurrently? Or is the spell more specific than the infusion, and so creates the case of specific trumping general? The spell seems to refer to itself when talking about homunculi(?), which is what begged the question.