Well I got two sense to add to this thread, I haven't written any books, I have not done all or anything that the main stream books and topics suggest, I did it backwards.. most of what I have done with photography is backwards from the traditional approach.
I threw my light meter away in 1973 and havent used one since. Learn how to READ............."light" !
BUT.. .. I HAVE HONESTLY MADE a ton of money from my hobby ! and enough to retire a full time job and my photos continiue to sell BIG TIME very cheap. and I make more $$ than your average pro would or could ever make !
I do things different !
A few case examples of how I think and work !
I am at work on a huge nuclear power plant under construction. I took a photo of what is called "BIG BLUE"
A HUGE construction crane (1979) you can see photos of this crane on google images. but not the one I captured and created.. I sure wish i had a copy of this.
3 bucks ! = 8 x 10 color print - $12,000 bucks in 3 months time.. true story !

each and every night I would process 100 8 x 10 prints at this sink using just two trays..Each and every morning at work I would drop off a box of prints at the tool shack for the carpenters (1000) and ironworkers (1000) in other words each craft or trade had 1000 workers on this huge project in hanford @ WPPSS.
by 9:30 coffee break that box would be empty !!
contstruction jobs are a great place to make money taking photographs. especially ironworkers. and every construction job needs photographs.. try taking photos of workers without them seeing you and then try and sell them to them CHEAP.. ironworkers are notorious for purchasing a half dozen or more if you catch them walking the high steel.. especially if you can get above them in a higher building next to them..
what do you really want to do in photography ?? make money or try and impress people with outrageous prices that no one will purchase.
Rather than sell two prints @ 100 each.. I much rather sell thousands of them @ 3 bucks each.! The cost at the time for ME to process and make 8 x 10 color prints
was about 37 cents. 25 cents for the actual sheet of kodak color paper and 17 - 22 cents for the chemicals I purchased. ( per print )
Kodak says that with practice 3 prints can be processed in a tray at once, by interleaving them and moving them one on top of the other during the development state. They also say that with MUCH PRACTICE six can be done at once, using the same technique. Well we were way beyond MUCH PRACTICE and were successfull in dumping 20 at a time.. at 5 second intervals into the tray..
5 runs and 100 prints were finished in under two hours time.! Print # 1 was the same density as print #100, due to proper replenish ment rates !
even now.. today.. I sell my photographs for 2 bucks ( postcards) and 2.50 for notecards.. 8 x 10's 5 - 10 bucks today.. and up for larger sized.
I make big money off of selling images all over the world in 33 countries when we first opened our gallery.. I am selling photographs that I created in 1982 and they still sell big time each and every year all over the state of Alaska and coutritnes all over the world.

what is the secret ? create an image that people WANT. sell thousands of them...
The real world does it different and they haven't yet caught on..
A wedding photographer requires a lot of work to make that 2,000 per wedding or 4,000 per wedding..
now if you can do 100 of those every year.. well you still have to continue to create to sell or make money..
for all practical purposes I haven't used a camera in almost 20 years. but the money comes in every year.
learning how to market your images and sell them is an art in itself.. I could easily fill pages with secrets to how to market your jmages all over the place. but you gotta do the work to get your work in front of people that can make this happen.
and you need a vast library of images to draw from and re-produce.
24" x 36" images are huge and wonderful to look at. but to purchase a photograph that size is in the 500 dollar or higher price range..
but to sell that same image for 20 bucks as A LITHO is going to get you a lot more customeres than selling photographs.!!!
you cannot stirke it rich using just one image.. you need lots of them. then to have color sepreatinos made and posters made is ging to cost you in the neighborhood of 2,500 dollars.. but 2,000 prints @ 20 bucks each = 40 K !!
now if you have 100 images to slowly build up your inventory.. soon.. after you get this working and established and slowly build up your inventory YOUR GOING TO MAKE A TON OF MONEY DOING it this way....
if you can sell these images.. !!! that is the hard part.. where to sell , how to sell..
there are many options.. outdoor markets, flea markets, garage sales, are just a few.. opening your own small store/ gallery is much better.. !
placing post card stands in various locations is also a great way to gain exposure of your work to the public. Start out small.. YOU WILL GROW.. IT JUST TAKES TIME.
Having your Note-Card stand in a small store or airport or many other locations is another great way.. but you need 100 of them all over your state and beyond.. and then it all happens.. thousands of dollars daily as your products reach out and are visible in every location you can possibly purchase a "stand" for and supply the inventory for them.
ART = is different to anyone you ask. everyone has their own opinion as to what ART - entails or equals.. ! If you can sell it.. then it is ART no matter what it is.
I will show you just a few of the photos that make me Big bucks each and every year. they do not look special or exotic but they do sell BIG TIME every year and these were created almost 30 years ago !!! but they sell every year all year !

I hope I have provided something for you to think about and to inspire you and motivate you.. it is very easy to make money in photography.. I have been doing it for decades.. I retired 11 years ago @ the young age of 48. My photos will continue to support my sons long after I am long gone.!!!
GOOD LUCK. pm me if you want more information !!