Can you earn a living as a writer?

There's no easy answer to this question.
Some can.
Some can not.  (me)
True confession - I make between $2,000 - $3,000 a year of writing income.
Some years less.
Some years more.
But there are other writers who have expanded their skills into other areas of income.

Here's a link to Laura Purdie Salas's yearly report(s) about how much she earns writing.
You'll notice that only a portion is made from writing trade books.
The rest comes from many other places. Places that  you might be interested in exploring is you want to expand your writing income.

She also has a link to another interesting article about the reality of six-figure book deals. Just in case you are dreaming about getting one of those.