Hey Derek
First, check this out to be sure of your understanding of broad, phrase and exact match: google documentation
I almost always use exact match to gauge search volume. A search for "how to be a freelance" counts as a broad match. Even "freelance" or "writer" counts as a broad match. These aren't relevant at all, so thus a very bad assessment of search volume.
Even phrase match is misleading. "Hire a freelance writer" could count as a phrase search, totally not relevant and therefore shouldn't count.
It is therefore, I ONLY want to know how many people are searching, exactly for "how to become a freelance writer". Its guarenteed to be that exact search, which guarentees relevance.
If you optimize and rank for "how to become a freelance writer" you may also rank for similar or related phrases, like "how to be a freelance writer" or "be a freelance writer".
Exact match is your best bet when judging search volume, because phrase and broad are way too unpredictable, as to whether the search variations are going to at all relevant.
So choose a good phrase with a decent amount of exact search volume, optimize for that, and you may also naturally rank for related long-tail more specific phrases as well - like "how to become a freelance writer from home", etc.
-Dan