I would be broke...
How much money would you earn if you played chess professionally

If you won,you could make a substantial amount of money in a international tournament.
I do not think many GMs can survive on price money. They take extra work. For example commenting, coaching, making tutorials.

The top players must make a decent figure, but for everyone else....meh. There are only so many good commentating jobs and Yasser and Maurice have those pretty much locked up. Maurice Ashley said in yesterdays broadcast of the US Championship that someone would have to hire a dedicated chess mentor to become titled. Playing and trying to figure out your own weaknesses yourself will set you back years. Eric Hansen said in order to pay a team like Fabio has around him, it would cost quite a lot. Probably not a lot of super GMs from a poverty household. Can someone make a lot playing chess? Yes, there are plenty of people killing it. It takes marketing yourself, right place, right time, and having consistent results and a rating that is always on the rise.
Possibly of interest:
"... the NM title is an honor that only one percent of USCF members attain. ..." - IM John Donaldson (2015)
http://www.jeremysilman.com/shop/pc/Reaching-the-Top-77p3905.htm
https://www.chess.com/article/view/can-anyone-be-an-im-or-gm
http://www.cbsnews.com/news/kids-fight-stereotypes-using-chess-in-rural-mississippi/
http://brooklyncastle.com/
"To become a grandmaster is very difficult and can take quite a long time! ... you need to ... solve many exercises, analyse your games, study classic games, modern games, have an opening repertoire and so on. Basically, it is hard work ... It takes a lot more than just reading books to become a grandmaster I am afraid." - GM Artur Yusupov (2013)
http://www.qualitychess.co.uk/ebooks/QandAwithArturYusupovQualityChessAugust2013.pdf
https://www.chess.com/blog/smurfo/book-review-insanity-passion-and-addiction
http://www.nytimes.com/1988/09/26/books/books-of-the-times-when-the-child-chess-genius-becomes-the-pawn.html
https://www.forbes.com/sites/alexknapp/2017/05/05/making-a-living-in-chess-is-tough-but-the-internet-is-making-it-easier/#4284e4814850
https://www.chess.com/news/view/is-there-good-money-in-chess-1838
"... Many aspiring young chess players dream of one day becoming a grandmaster and a professional. ... But ... a profession must bring in at least a certain regular income even if one is not too demanding. ... The usual prize money in Open tournaments is meagre. ... The higher the prizes, the greater the competition. ... With a possibly not very high and irregular income for several decades the amount of money one can save for old age remains really modest. ... Anyone who wants to reach his maximum must concentrate totally on chess. That involves important compromises with or giving up on his education. ... it is a question of personal life planning and when deciding it is necessary to be fully conscious of the various possibilities, limitations and risks. ... a future professional must really love chess and ... be prepared to work very hard for it. ... It is all too frequent that a wrong evaluation is made of what a talented player can achieve. ... Most players have the potential for a certain level; once they have reached it they can only make further progress with a great effort. ... anyone who is unlikely to attain a high playing strength should on no account turn professional. ... Anyone who does not meet these top criteria can only try to earn his living with public appearances, chess publishing or activity as a trainer. But there is a lack of offers and these are not particularly well paid. For jobs which involve appearing in public, moreover, certain non-chess qualities are required. ... a relevant 'stage presence' and required sociability. ... All these jobs and existences, moreover, have hanging above them the sword of Damocles of general economic conditions. ... around [age] 40 chess players ... find that their performances are noticeably tailing off. ..." - from a 12 page chapter on becoming a chess professional in the book, Luther's Chess Reformation by GM Thomas Luther (2016)
http://www.qualitychess.co.uk/ebooks/LuthersChessReformation-excerpt.pdf

If you won,you could make a substantial amount of money in a international tournament.
I do not think many GMs can survive on price money. They take extra work. For example commenting, coaching, making tutorials.
Also, I think your national federation may pay you.

I think I could easily make several dollars a day if I set up in Harvard Square with a sign "Beat the patzer; improve your self esteem. $1." That counts as a chess professional, right?

A tiny few are absolutely minting it, while a couple of handfuls make a very decent living. The rest can probably be placed in the category that Thomas Luther describes. He speaks a lot of sense on this issue. It's worth noting, for instance, that even such a succesful player as Wesley So, for reasons of cost, conducted nearly all his training sessions with Vladimir Tukmakov via Skype.

I think I could easily make several dollars a day if I set up in Harvard Square with a sign "Beat the patzer; improve your self esteem. $1." That counts as a chess professional, right?
Beat the patzer; improve your self esteem. $1.
Profanity and insults allowed. $2.
(I could potentially make double your income.) :)
?