"My brother wants to be an engineer."
Translation:Mon frère veut être un ingénieur.
But aren't careers always treated as adjectives when etre and indirect articles are involved, and therefore don't take an indirect article ever? Direct articles are fine though. If I'm wrong, please let me know, but I distinctly remember my teacher one year threatening to throw chalk at whoever made that mistake again.
I checked several grammar sites and they say that you should not use the indefinite article between the verb "être" and a profession. For example: http://french.about.com/od/vocabulary/a/professions.htm http://www.learn-french-help.com/indefinite-article.html
I will comment that this seems wrong and if it is technically correct ask that they (1) have a native speaker join this discussion and explain the rule and (2) correct the rest of the lessons to accept "un" or "une" between "être" and a profession.
Pretty close in common usage, but the meaning is not exactly the same - "to become" implies the process of becoming a lawyer - law school, bar exams, etc. "To be" is focused on the final state. Real life example - last night at dinner my daughter said she wants to be a lawyer. What she doesn't want is to go to law school or study for exams. :-)