"I want to become a nurse."
Translation:Mi volas fariĝi flegisto.
The way I remember this is that verbs which have to do with variants on "being" (of which "becoming" is one) behave like "esti" in not using the accusative.
- I want to become a nurse ~= I want, at some time, to be a nurse
- mi volas fariĝi flegisto ~= mi volas iam esti flegisto
The examples in https://en.wikipedia.org/wiki/Esperanto_grammar#Nouns_and_adjectives are also relevant:
- mi farbis la pordon ruĝan (I painted the red door)
- mi farbis la pordon ruĝa (I painted the door red).
I try to hear the second one as something like "I painted the door to be red" and that reminds me the accusative doesn't happen there.