Is there a single word describing earning money through any means?

Perhaps the exquisite and rare adjective "quomodocunquizing" will suit your need. And, it does not have negative overtone, it is very much neutral. You can use it in all possible registers: greedy politicians, greedy businessmen, greedy youngster, greedy person, or greedy society etc. You can also use it in your essay title. It is an adjective defined as,

that makes money in any possible way

Merriam Webster referes it as an archaic (and not obsolete) word. Check side note: https://www.merriam-webster.com/words-at-play/patriotism-vs-nationalism

So, if you are driven by the desire to accumulate wealth by hook or by crook you are an "quomodocunquizing person". You don't have to be a criminal or mafia to do so, you can be quomodocunquizing businessman.

Also, if you prefer, then you can use materialistic. It is an adjective and has a somewhat negative connotation.It is a synonym of "money-oriented". Being a materialistic or money-oriented isn't an acute negative thing in the contemporary world, isn't it?

Merriam Webster: https://www.merriam-webster.com/dictionary/materialistic

excessively concerned with material possessions; money-oriented.

"we're living in a highly materialistic society"

Reference link for the word: quomodocunquizing

citation 1: Official twitter of Oxford English Dictionary

citation 2: New York Times - Daily Lexeme

citation 3: Book- There's a Word for It (Revised Edition): A Grandiloquent Guide to Life

citation 4: Book- The Horologicon By Mark Forsyth

"Mercenary", as an adjective, means exactly what you describe: a person focused on making money, allowing this priority to override any moral concerns or ethics. (And being "ready to earn money even in the middle of war" is exactly the source of the word; but it can be applied to people in any context, not only soldiers of fortune.)

Oxford dictionaries has the definition as "Primarily concerned with making money at the expense of ethics."

The OED gives this definition for the adjective "mercenary":

1. a. Of a person, organization, etc.: working or acting merely for money or other material reward; motivated by self-interest; materialistic.
   b. Of conduct, a course of action, etc., or its motivation: characterized by self-interest or the pursuit of personal gain; prompted by the desire for money or other material reward; undertaken only for personal gain.